Anti-FcRn Antibodies

ABSTRACT

The disclosure relates to antibodies specific to FcRn, formulations comprising the same, use of each in therapy, processes for expressing and optionally formulating said antibody, DNA encoding the antibodies and hosts comprising said DNA.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Divisional application under 35 U.S.C. §120 of U.S. application Ser. No. 16/271,086, filed Feb. 8, 2019, whichis a Divisional application under 35 U.S.C. § 120 of U.S. applicationSer. No. 14/400,812, filed Nov. 13, 2014, now U.S. Pat. No. 10,233,243,issued Mar. 19, 2019, which is the U.S. National Phase under 35 U.S.C. §371 of PCT International Application No. PCT/EP2013/059802, filed May13, 2013, which claims the benefit of priority under 35 U.S.C. § 119(a)of British Application No. 1208370.5, filed May 14, 2012, all of whichare incorporated herein by reference in their entirety. The disclosurerelates to antibodies specific to FcRn, formulations comprising thesame, use of each in therapy, processes for expressing and optionallyformulating said antibody, DNA encoding the antibodies and hostscomprising said DNA.

FcRn is a non-covalent complex of membrane protein FcRn a chain and (32microglobulin (132M). In adult mammals FcRn plays a key role inmaintaining serum antibody levels by acting as a receptor that binds andsalvages antibodies of the IgG isotype. IgG molecules are endocytosed byendothelial cells, and if they bind to FcRn, are recycled transcytosedout into, for example circulation. In contrast, IgG molecules that donot bind to FcRn enter the cells and are targeted to the lysosomalpathway where they are degraded. A variant IgG1 in which His435 ismutated to alanine results in the selective loss of FcRn binding and asignificantly reduced serum half-life (Firan et al. 2001, InternationalImmunology 13:993).

It is hypothesised that FcRn is a potential therapeutic target forcertain autoimmune disorders caused at least in part by autoantibodies.The current treatment for certain such disorders includesplasmapheresis. Sometimes the plasmapheresis is employed along withimmunosuppressive therapy for long-term management of the disease.Plasma exchange offers the quickest short-term answer to removingharmful autoantibodies. However, it may also be desirable to suppressthe production of autoantibodies by the immune system for example by theuse of medications such as prednisone, cyclophosphamide, cyclosporine,mycophenolate mofetil, rituximab or a mixture of these.

Examples of diseases that can be treated with plasmapheresis include:Guillain-Barré syndrome; Chronic inflammatory demyelinatingpolyneuropathy; Goodpasture's syndrome; hyperviscosity syndromes;cryoglobulinemia; paraproteinemia; Waldenstrom macroglobulinemia;myasthenia gravis; thrombotic thrombocytopenic purpura (TTP)/hemolyticuremic syndrome; Wegener's granulomatosis; Lambert-Eaton Syndrome;antiphospholipid antibody syndrome (APS or APLS); microscopicpolyangiitis; recurrent focal and segmental glomerulosclerosis in thetransplanted kidney; HELLP syndrome; PANDAS syndrome; Refsum disease;Behcet syndrome; HIV-related neuropathy; Graves' disease in infants andneonates; pemphigus vulgaris; multiple sclerosis, rhabdomyolysis andalloimune diseases.

Plasmapheresis is sometimes used as a rescue therapy for removal of Fccontaining therapeutics, for example in emergencies to reduced seriousside effects.

Though plasmapheresis is helpful in certain medical conditions there arepotential risks and complications associated with the therapy. Insertionof a rather large intravenous catheter can lead to bleeding, lungpuncture (depending on the site of catheter insertion), and, if thecatheter is left in too long, it can lead to infection and/or damage tothe veins giving limited opportunity to repeat the procedure.

The procedure has further complications associated with it, for examplewhen a patient's blood is outside of the body passing through theplasmapheresis instrument, the blood has a tendency to clot. To reducethis tendency, in one common protocol, citrate is infused while theblood is running through the circuit. Citrate binds to calcium in theblood, calcium being essential for blood to clot. Citrate is veryeffective in preventing blood from dotting; however, its use can lead tolife-threateningly low calcium levels. This can be detected using theChvostek's sign or Trousseau's sign. To prevent this complication,calcium is infused intravenously while the patient is undergoing theplasmapheresis; in addition, calcium supplementation by mouth may alsobe given.

Other complications of the procedure include: hypotension; potentialexposure to blood products, with risk of transfusion reactions ortransfusion transmitted diseases, suppression of the patient's immunesystem and bleeding or hematoma from needle placement.

Additionally facilities that provide plasmapheresis are limited and theprocedure is very expensive.

An alternative to plasmapheresis is intravenous immunoglobulin (IVIG),which is a blood product containing pooled polyclonal IgG extracted fromthe plasma of over one thousand blood donors. The therapy isadministered intravenously and lasts in the region of 2 weeks to 3months.

Complications of the IVIG treatment include headaches, dermatitis, viralinfection from contamination of the therapeutic product, for example HIVor hepatitis, pulmonary edema, allergic reactions, acute renal failure,venous thrombosis and aseptic meningitis.

Thus there is a significant unmet need for therapies for autoimmunedisorders which are less invasive and which expose the patients to lessmedical complications.

Thus there is a significant unmet need for therapies for immunologicaldisorders and/or autoimmune disorders which are less invasive and whichexpose the patients to less medical complications.

Accordingly agents that block or reduce the binding of IgG to FcRn maybe useful in the treatment or prevention of such autoimmune andinflammatory diseases. Anti-FcRn antibodies have been describedpreviously in WO2009/131702, WO2007/087289 and WO2006/118772.

However, there remains a need for improved anti-FcRn antibodies.

SUMMARY OF THE DISCLOSURE

Thus in one aspect there is provided an anti-FcRn antibody or bindingfragment thereof comprising a heavy chain or heavy chain fragment havinga variable region, wherein said variable region comprises one, two orthree CDRs independently selected from SEQ ID NO: 1, SEQ ID NO: 2 andSEQ ID NO: 3, for example wherein CDR H1 is SEQ ID NO: 1, CDR H2 is SEQID NO: 2 and CDR H3 is SEQ ID NO: 3.

In another aspect there is provided an antibody or fragment comprising asequence or combinations of sequences as defined herein, for example acognate pair variable region.

The antibodies of the disclosure block binding of IgG to FcRn and arethought to be useful in reducing one or more biological functions ofFcRn, including reducing half-life of circulating antibodies. This maybe beneficial in that it allows the patient to more rapidly clearantibodies, such as autoantibodies.

Importantly the antibodies of the present invention are able to bindhuman FcRn at both pH6 and pH7.4 with comparable and high bindingaffinity. Advantageously therefore the antibodies are able to continueto bind FcRn even within the endosome, thereby maximising the blockingof FcRn binding to IgG, see FIG. 10 for an illustration of themechanism.

In one embodiment the antibodies or binding fragments according to thepresent disclosure comprise a light chain or light chain fragment havinga variable region, for example comprising one, two or three CDRsindependently selected from SEQ ID NO: 4, SEQ ID NO: 5 and SEQ ID NO: 6,in particular wherein CDR L1 is SEQ ID NO: 4, CDR L2 is SEQ ID NO: 5 andCDR L3 is SEQ ID NO: 6.

In one embodiment the antibodies or binding fragments according to thepresent disclosure comprise CDR sequences of SEQ ID NOs: 1 to 6, forexample wherein CDR H1 is SEQ ID NO: 1, CDR H2 is SEQ ID NO: 2, CDR H3is SEQ ID NO: 3, CDR L1 is SEQ ID NO: 4, CDR L2 is SEQ ID NO: 5 and CDRL3 is SEQ ID NO: 6.

The disclosure also extends to a polynucleotide, such as DNA, encodingan antibody or fragment as described herein.

Also provided is a host cell comprising said polynucleotide.

Methods of expressing an antibody or fragment are provided herein as aremethods of conjugating an antibody or fragment to a polymer, such asPEG.

The present disclosure also relates to pharmaceutical compositionscomprising said antibodies and fragments.

In one embodiment there is provided a method of treatment comprisingadministering a therapeutically effective amount of an antibody,fragment or composition as described herein.

The present disclosure also extends to an antibody, fragment orcomposition according to the present disclosure for use in treatment,particularly in the treatment of an immunological and/or autoimmunedisorder.

Thus the present disclosure provides antibodies, fragments thereof andmethods for removal of pathogenic IgG, which is achieved by acceleratingthe body's natural mechanism for catabolising IgG.

In essence the antibodies and fragments according to the disclosureblock the system that recycles IgG in the body.

The present therapy is likely to provide a replacement or supplement forcertain diseases where plasmapheresis is a therapy or IVIg therapy,which is advantageous for patients.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1 and 1A-1FF shows certain amino acid and polynucleotidesequences.

FIGS. 2A-2B shows alignments of certain sequences.

FIGS. 3A-3B shows a comparison of binding on human MDCK II for a Fab′fragment according to the present disclosure and a PEGylated versionthereof

FIG. 4 shows a Fab′ fragment according to the present disclosure and aPEGylated version thereof inhibiting IgG recycling on MDCK II cells

FIG. 5 shows a PEGylated Fab′ fragment according to the presentdisclosure inhibits apical to basolateral IgG trancytosis in MDCK IIcells

FIGS. 6A-6B shows a comparison of binding of cyno monkey MDCK II for aFab′ fragment according to the present disclosure and a PEGylatedversion thereof

FIG. 7 shows a PEGylated Fab′ fragment according to the presentinhibiting IgG recycling on MDCK II cells for human and cyno monkeyversions thereof

FIG. 8 shows the effect of a single dose of a PEGylated Fab′ moleculeaccording to the disclosure on plasma IgG levels in cynomolgus monkeys

FIG. 9 shows the effect of four weekly doses of a PEGylated Fab′molecule according to the disclosure on plasma IgG levels

FIG. 10 shows a diagrammatic representation of antibody recyclingfunction of FcRn inhibited by a blocking protein

FIG. 11 shows flow cytometry based human IgG blocking assay usingpurified gamma 1 IgG antibodies

FIG. 12 shows Fab′PEG single/intermittent IV doses in normal cyno 20mg/Kg days 1 and 67 IgG pharmacodynamics

FIG. 13 shows Fab′PEG: repeat IV doses in normal cyno-4×20 or 100 mg/Kgper week IgG pharmacodynamics

FIG. 14 shows Fab′PEG single/intermittent IV doses in normal cyno −20mg/Kg and 100 mg/Kg days 1 and 67 IgG Pharmacodynamics

FIG. 15 shows plasma IgG levels in 4 cynomolgus monkeys after 2 IV dosesof 20 mg/Kg 1519.g57 Fab′PEG

FIG. 16 shows plasma IgG levels in 4 cynomolgus monkeys receiving 10 IVdoses of 20 mg/Kg 1519.g57 Fab′PEG, one every 3 days

FIG. 17 shows the effect of two 30 mg/Kg IV doses of 1519.g57 IgG4P onthe endogenous plasma IgG in cynomolgus monkeys

FIG. 18 shows the effect of 30 mg/Kg if followed by 41 daily doses of 5mg/Kg 1519.g57 IgG4P on plasma IgG in cynomolgus monkeys

FIG. 19 shows the result of daily dosing with vehicle on the plasma IgGin cynomolgus monkeys

FIG. 20 shows the increased clearance of IV hIgG in plasma of hFcRntransgenic mice treated with CA170_01519.g57 Fab′PEG or PBS IV

FIG. 21 shows the increased clearance of IV hIgG in plasma of hFcRntransgenic mice treated with CA170_01519.g57 IgG1 or IgG4 or PBS IV

FIG. 22 shows the increased clearance of IV hIgG in plasma of hFcRntransgenic mice treated with CA170_01519.g57 Fab′-human serum albumin orPBS IV

FIG. 23 shows the increased clearance of IV hIgG in plasma of hFcRntransgenic mice treated with CA170_01519.g57 FabFv or PBS IV

FIG. 24 shows the increased clearance of IV hIgG in plasma of hFcRntransgenic mice treated with CA170_01519.g57 Fab or Fab′PEG or PBS IV

FIG. 25 shows a bispecific antibody fusion protein of the presentinvention, referred to as a Fab-dsFv.

FIG. 26 shows pictures of the crystals in a drop and frozen.

DETAILS OF THE DISCLOSURE

FcRn as employed herein refers to the non-covalent complex between thehuman IgG receptor alpha chain, also known as the neonatal Fc receptor,the amino acid sequence of which is in UniProt under number P55899together with β2 microglobulin (β2M), the amino acid sequence of whichis in UniProt under number P61769.

Antibody molecule as employed herein refers to an antibody or bindingfragment thereof.

The term ‘antibody’ as used herein generally relates to intact (whole)antibodies i.e. comprising the elements of two heavy chains and twolight chains. The antibody may comprise further additional bindingdomains for example as per the molecule DVD-Ig as disclosed in WO2007/024715, or the so-called (FabFv)₂Fc described in WO2011/030107.Thus antibody as employed herein includes bi, tri or tetra-valent fulllength antibodies.

Binding fragments of antibodies include single chain antibodies (i.e. afull length heavy chain and light chain); Fab, modified Fab, Fab′,modified Fab′, F(ab′)2, Fv, Fab-Fv, Fab-dsFv, single domain antibodies(e.g. VH or VL or VHH), scFv, bi, tri or tetra-valent antibodies,Bis-scFv, diabodies, tribodies, triabodies, tetrabodies andepitope-binding fragments of any of the above (see for example Holligerand Hudson, 2005, Nature Biotech. 23(9):1126-1136; Adair and Lawson,2005, Drug Design Reviews—Online 2(3), 209-217). The methods forcreating and manufacturing these antibody fragments are well known inthe art (see for example Verma et al., 1998, Journal of ImmunologicalMethods, 216, 165-181). The Fab-Fv format was first disclosed inWO2009/040562 and the disulphide stabilised versions thereof, theFab-dsFv was first disclosed in WO2010/035012, see also FIG. 25 herein.Other antibody fragments for use in the present invention include theFab and Fab′ fragments described in International patent applicationsWO2005/003169, WO2005/003170 and WO2005/003171. Multi-valent antibodiesmay comprise multiple specificities e.g. bispecific or may bemonospecific (see for example WO 92/22583 and WO05/113605). One suchexample of the latter is a Tri-Fab (or TFM) as described in WO92/22583.

A typical Fab′ molecule comprises a heavy and a light chain pair inwhich the heavy chain comprises a variable region V_(H), a constantdomain C_(H)1 and a natural or modified hinge region and the light chaincomprises a variable region V_(L) and a constant domain C_(L).

In one embodiment there is provided a dimer of a Fab′ according to thepresent disclosure to create a F(ab′)₂ for example dimerisation may bethrough the hinge.

In one embodiment the antibody or binding fragment thereof comprises abinding domain. A binding domain will generally comprises 6 CDRs, threefrom a heavy chain and three from a light chain. In one embodiment theCDRs are in a framework and together form a variable region. Thus in oneembodiment an antibody or binding fragment comprises a binding domainspecific for antigen comprising a light chain variable region and aheavy chain variable region.

It will be appreciated that one or more (for example 1, 2, 3 or 4) aminoacid substitutions, additions and/or deletions may be made to the CDRsor other sequences (e.g variable domains) provided by the presentinvention without significantly altering the ability of the antibody tobind to FcRn. The effect of any amino acid substitutions, additionsand/or deletions can be readily tested by one skilled in the art, forexample by using the methods described herein, in particular in theExamples, to determine FcRn.

In one or more (for example 1, 2, 3 or 4) amino acid substitutions,additions and/or deletions may be made to the framework region employedin the antibody or fragment provided by the present invention andwherein binding affinity to FcRn is retained or increased.

The residues in antibody variable domains are conventionally numberedaccording to a system devised by Kabat et al. This system is set forthin Kabat et al., 1987, in Sequences of Proteins of ImmunologicalInterest, US Department of Health and Human Services, NIH, USA(hereafter “Kabat et al. (supra)”). This numbering system is used in thepresent specification except where otherwise indicated.

The Kabat residue designations do not always correspond directly withthe linear numbering of the amino acid residues. The actual linear aminoacid sequence may contain fewer or additional amino acids than in thestrict Kabat numbering corresponding to a shortening of, or insertioninto, a structural component, whether framework or complementaritydetermining region (CDR), of the basic variable domain structure. Thecorrect Kabat numbering of residues may be determined for a givenantibody by alignment of residues of homology in the sequence of theantibody with a “standard” Kabat numbered sequence.

The CDRs of the heavy chain variable domain are located at residues31-35 (CDR-H1), residues 50-65 (CDR-H2) and residues 95-102 (CDR-H3)according to the Kabat numbering system. However, according to Chothia(Chothia, C. and Lesk, A. M. J. Mol. Biol., 196, 901-917 (1987)), theloop equivalent to CDR-H1 extends from residue 26 to residue 32. Thusunless indicated otherwise ‘CDR-H1’ as employed herein is intended torefer to residues 26 to 35, as described by a combination of the Kabatnumbering system and Chothia's topological loop definition.

The CDRs of the light chain variable domain are located at residues24-34 (CDR-L1), residues 50-56 (CDR-L2) and residues 89-97 (CDR-L3)according to the Kabat numbering system.

Antibodies and fragments of the present disclosure block FcRn and maythereby prevent it functioning in the recycling of IgG. Blocking asemployed herein refers to physically blocking such as occluding thereceptor but will also include where the antibody or fragments binds anepitope that causes, for example a conformational change which meansthat the natural ligand to the receptor no longer binds. Antibodymolecules of the present invention bind to FcRn and thereby decrease orprevent (e.g. inhibit) FcRn binding to an IgG constant region.

In one embodiment the antibody or fragment thereof binds FcRncompetitively with respect to IgG.

In one example the antibody or binding fragment thereof functions as acompetitive inhibitor of human FcRn binding to human IgG. In one examplethe antibody or binding fragment thereof binds to the IgG binding siteon FcRn. In one example the antibody or binding fragment thereof doesnot bind 132M.

Antibodies for use in the present disclosure may be obtained using anysuitable method known in the art. The FcRn polypeptide/protein includingfusion proteins, cells (recombinantly or naturally) expressing thepolypeptide (such as activated T cells) can be used to produceantibodies which specifically recognise FcRn. The polypeptide may be the‘mature’ polypeptide or a biologically active fragment or derivativethereof. The human protein is registered in Swiss-Prot under the numberP55899. The extracellular domain of human FcRn alpha chain is providedin SEQ ID NO:94. The sequence of (32M is provided in SEQ ID NO:95.

In one embodiment the antigen is a mutant form of FcRn which isengineered to present FcRn on the surface of a cell, such that there islittle or no dynamic processing where the FcRn is internalised in thecell, for example this can be achieved by making a mutation in thecytoplasmic tail of the FcRn alpha chain, wherein di-leucine is mutatedto di-alanine as described in Ober et al 2001 Int. Immunol. 13,1551-1559.

Polypeptides, for use to immunize a host, may be prepared by processeswell known in the art from genetically engineered host cells comprisingexpression systems or they may be recovered from natural biologicalsources. In the present application, the term “polypeptides” includespeptides, polypeptides and proteins. These are used interchangeablyunless otherwise specified. The FcRn polypeptide may in some instancesbe part of a larger protein such as a fusion protein for example fusedto an affinity tag or similar.

Antibodies generated against the FcRn polypeptide may be obtained, whereimmunisation of an animal is necessary, by administering thepolypeptides to an animal, preferably a non-human animal, usingwell-known and routine protocols, see for example Handbook ofExperimental Immunology, D. M. Weir (ed.), Vol 4, Blackwell ScientificPublishers, Oxford, England, 1986). Many warm-blooded animals, such asrabbits, mice, rats, sheep, cows, camels or pigs may be immunized.However, mice, rabbits, pigs and rats are generally most suitable.

Monoclonal antibodies may be prepared by any method known in the artsuch as the hybridoma technique (Kohler & Milstein, 1975, Nature,256:495-497), the trioma technique, the human B-cell hybridoma technique(Kozbor et al., 1983, Immunology Today, 4:72) and the EBV-hybridomatechnique (Cole et al., Monoclonal Antibodies and Cancer Therapy, pp77-96, Alan R Liss, Inc., 1985).

Antibodies for use in the invention may also be generated using singlelymphocyte antibody methods by cloning and expressing immunoglobulinvariable region cDNAs generated from single lymphocytes selected for theproduction of specific antibodies by, for example, the methods describedby Babcook, J. et al., 1996, Proc. Natl. Acad. Sci. USA93(15):7843-78481; WO92/02551; WO2004/051268 and International PatentApplication number WO2004/106377.

Screening for antibodies can be performed using assays to measurebinding to human FcRn and/or assays to measure the ability to block IgGbinding to the receptor. An example of a binding assay is an ELISA, inparticular, using a fusion protein of human FcRn and human Fc, which isimmobilized on plates, and employing a secondary antibody to detectanti-FcRn antibody bound to the fusion protein. Examples of suitableantagonistic and blocking assays are described in the Examples herein.

Humanised antibodies (which include CDR-grafted antibodies) are antibodymolecules having one or more complementarity determining regions (CDRs)from a non-human species and a framework region from a humanimmunoglobulin molecule (see, e.g. U.S. Pat. No. 5,585,089; WO91/09967).It will be appreciated that it may only be necessary to transfer thespecificity determining residues of the CDRs rather than the entire CDR(see for example, Kashmiri et al., 2005, Methods, 36, 25-34). Humanisedantibodies may optionally further comprise one or more frameworkresidues derived from the non-human species from which the CDRs werederived. The latter are often referred to as donor residues.

Specific as employed herein is intended to refer to an antibody thatonly recognises the antigen to which it is specific or an antibody thathas significantly higher binding affinity to the antigen to which it isspecific compared to binding to antigens to which it is non-specific,for example at least 5, 6, 7, 8, 9, 10 times higher binding affinity.Binding affinity may be measured by techniques such as BIAcore asdescribed herein below. In one example the antibody of the presentinvention does not bind (32 microglobulin (132M). In one example theantibody of the present invention binds cynomolgus FcRn. In one examplethe antibody of the present invention does not bind rat or mouse FcRn.

The amino acid sequences and the polynucleotide sequences of certainantibodies according to the present disclosure are provided in theFigures.

In one embodiment the antibody or fragments according to the disclosureare humanised.

As used herein, the term ‘humanised antibody molecule’ refers to anantibody molecule wherein the heavy and/or light chain contains one ormore CDRs (including, if desired, one or more modified CDRs) from adonor antibody (e.g. a non-human antibody such as a murine monoclonalantibody) grafted into a heavy and/or light chain variable regionframework of an acceptor antibody (e.g. a human antibody). For a review,see Vaughan et al, Nature Biotechnology, 16, 535-539, 1998. In oneembodiment rather than the entire CDR being transferred, only one ormore of the specificity determining residues from any one of the CDRsdescribed herein above are transferred to the human antibody framework(see for example, Kashmiri et al., 2005, Methods, 36, 25-34). In oneembodiment only the specificity determining residues from one or more ofthe CDRs described herein above are transferred to the human antibodyframework. In another embodiment only the specificity determiningresidues from each of the CDRs described herein above are transferred tothe human antibody framework.

When the CDRs or specificity determining residues are grafted, anyappropriate acceptor variable region framework sequence may be usedhaving regard to the class/type of the donor antibody from which theCDRs are derived, including mouse, primate and human framework regions.

Suitably, the humanised antibody according to the present invention hasa variable domain comprising human acceptor framework regions as well asone or more of the CDRs provided specifically herein. Thus, provided inone embodiment is blocking humanised antibody which binds human FcRnwherein the variable domain comprises human acceptor framework regionsand non-human donor CDRs.

Examples of human frameworks which can be used in the present inventionare KOL, NEWM, REI, EU, TUR, TEI, LAY and POM (Kabat et al., supra). Forexample, KOL and NEWM can be used for the heavy chain, REI can be usedfor the light chain and EU, LAY and POM can be used for both the heavychain and the light chain. Alternatively, human germline sequences maybe used; these are available at: vbase.mrc-cpe.cam.ac.uk/In a humanisedantibody of the present invention, the acceptor heavy and light chainsdo not necessarily need to be derived from the same antibody and may, ifdesired, comprise composite chains having framework regions derived fromdifferent chains.

One such suitable framework region for the heavy chain of the humanisedantibody of the present invention is derived from the human sub-groupVH3 sequence 1-3 3-07 together with JH4 (SEQ ID NO: 56).

Accordingly, in one example there is provided a humanised antibodycomprising the sequence given in SEQ ID NO: 1 for CDR-H1, the sequencegiven in SEQ ID NO: 2 for CDR-H2 and the sequence given in SEQ ID NO: 3for CDRH3, wherein the heavy chain framework region is derived from thehuman subgroup VH3 sequence 1-3 3-07 together with JH4.

The sequence of human JH4 is as follows: (YFDY)WGQGTLVTVS (Seq ID No:70). The YFDY motif is part of CDR-H3 and is not part of framework 4(Ravetch, J V. et al., 1981, Cell, 27, 583-591).

In one example the heavy chain variable domain of the antibody comprisesthe sequence given in SEQ ID NO: 29.

A suitable framework region for the light chain of the humanisedantibody of the present invention is derived from the human germlinesub-group VK1 sequence 2-1-(1) A30 together with JK2 (SEQ ID NO: 54).

Accordingly, in one example there is provided a humanised antibodycomprising the sequence given in SEQ ID NO: 4 for CDR-L1, the sequencegiven in SEQ ID NO: 5 for CDR-L2 and the sequence given in SEQ ID NO: 6for CDRL3, wherein the light chain framework region is derived from thehuman subgroup VK1 sequence 2-1-(1) A30 together with JK2.

The JK2 sequence is as follows: (YT)FGQGTKLEIK (Seq ID No: 71). The YTmotif is part of CDR-L3 and is not part of framework 4 (Hieter, P A., etal., 1982, J. Biol. Chem., 257, 1516-1522).

In one example the light chain variable domain of the antibody comprisesthe sequence given in SEQ ID NO: 15.

In a humanised antibody of the present invention, the framework regionsneed not have exactly the same sequence as those of the acceptorantibody. For instance, unusual residues may be changed to morefrequently-occurring residues for that acceptor chain class or type.Alternatively, selected residues in the acceptor framework regions maybe changed so that they correspond to the residue found at the sameposition in the donor antibody (see Reichmann et al., 1998, Nature, 332,323-324). Such changes should be kept to the minimum necessary torecover the affinity of the donor antibody. A protocol for selectingresidues in the acceptor framework regions which may need to be changedis set forth in WO91/09967.

Thus in one embodiment 1, 2, 3, 4, or 5 residues in the framework arereplaced with an alternative amino acid residue.

Accordingly, in one example there is provided a humanised antibody,wherein at least the residues at each of positions 3, 24, 76, 93 and 94of the variable domain of the heavy chain (Kabat numbering) are donorresidues, see for example the sequence given in SEQ ID NO:

29.

In one embodiment residue 3 of the heavy chain variable domain isreplaced with an alternative amino acid, for example glutamine.

In one embodiment residue 24 of the heavy chain variable domain isreplaced with an alternative amino acid, for example alanine.

In one embodiment residue 76 of the heavy chain variable domain isreplaced with an alternative amino acid, for example asparagine.

In one embodiment residue 93 of the heavy chain is replaced with analternative amino acid, for example alanine.

In one embodiment residue 94 of the heavy chain is replaced with analternative amino acid, for example arginine.

In one embodiment residue 3 is glutamine, residue 24 is alanine, residue76 is aspargine, residue 93 is alanine and residue 94 is arginine in thehumanised heavy chain variable region according to the presentdisclosure.

Accordingly, in one example there is provided a humanised antibody,wherein at least the residues at each of positions 36, 37 and 58 of thevariable domain of the light chain (Kabat numbering) are donor residues,see for example the sequence given in SEQ ID NO: 15

In one embodiment residue 36 of the light chain variable domain isreplaced with an alternative amino acid, for example tyrosine.

In one embodiment residue 37 of the light chain variable domain isreplaced with an alternative amino acid, for example glutamine.

In one embodiment residue 58 of the light chain variable domain isreplaced with an alternative amino acid, for example valine.

In one embodiment residue 36 is tyrosine, residue 37 is glutamine andresidue 58 is valine, in the humanised heavy chain variable regionaccording to the present disclosure.

In one embodiment the disclosure provides an antibody sequence which is80% similar or identical to a sequence disclosed herein, for example85%, 90%, 91%, 92%, 93%, 94%, 95% 96%, 97%, 98% or 99% over part orwhole of the relevant sequence, for example a variable domain sequence,a CDR sequence or a variable domain sequence, excluding the CDRs. In oneembodiment the relevant sequence is SEQ ID NO: 15. In one embodiment therelevant sequence is SEQ ID NO: 29.

In one embodiment, the present invention provides an antibody moleculewhich binds human FcRn comprising a heavy chain, wherein the variabledomain of the heavy chain comprises a sequence having at least 80%, 85%,90%, 91%, 92%, 93%, 94%, 95% 96%, 97%, 98% or 99% identity or similarityto the sequence given in SEQ ID NO:29.

In one embodiment, the present invention provides an antibody moleculewhich binds human FcRn comprising a light chain, wherein the variabledomain of the light chain comprises a sequence having at least 80%, 85%,90%, 91%, 92%, 93%, 94%, 95% 96%, 97%, 98% or 99% identity or similarityto the sequence given in SEQ ID NO:15.

In one embodiment the present invention provides an antibody moleculewhich binds human FcRn wherein the antibody has a heavy chain variabledomain which is at least 90%, 91%, 92%, 93%, 94%, 95% 96%, 97%, 98% or99% similar or identical to the sequence given in SEQ ID NO:29 butwherein the antibody molecule has the sequence given in SEQ ID NO: 1 forCDR-H1, the sequence given in SEQ ID NO: 2 for CDR-H2 and the sequencegiven in SEQ ID NO: 3 for CDR-H3.

In one embodiment the present invention provides an antibody moleculewhich binds human FcRn wherein the antibody has a light chain variabledomain which is at least 90%, 91%, 92%, 93%, 94%, 95% 96%, 97%, 98% or99% similar or identical to the sequence given in SEQ ID NO:15 butwherein the antibody molecule has the sequence given in SEQ ID NO: 4 forCDR-L1, the sequence given in SEQ ID NO: 5 for CDR-L2 and the sequencegiven in SEQ ID NO:6 for CDR-L3.

In one embodiment the present invention provides an antibody moleculewhich binds human FcRn wherein the antibody has a heavy chain variabledomain which is at least 90%, 91%, 92%, 93%, 94%, 95% 96%, 97%, 98% or99% similar or identical to the sequence given in SEQ ID NO:29 and alight chain variable domain which is at least 90%, 91%, 92%, 93%, 94%,95% 96%, 97%, 98% or 99% similar or identical to the sequence given inSEQ ID NO:15 but wherein the antibody molecule has the sequence given inSEQ ID NO: 1 for CDR-H1, the sequence given in SEQ ID NO: 2 for CDR-H2,the sequence given in SEQ ID NO: 3 for CDR-H3, the sequence given in SEQID NO: 4 for CDR-L1, the sequence given in SEQ ID NO: 5 for CDR-L2 andthe sequence given in SEQ ID NO:6 for CDR-L3.

“Identity”, as used herein, indicates that at any particular position inthe aligned sequences, the amino acid residue is identical between thesequences. “Similarity”, as used herein, indicates that, at anyparticular position in the aligned sequences, the amino acid residue isof a similar type between the sequences. For example, leucine may besubstituted for isoleucine or valine. Other amino acids which can oftenbe substituted for one another include but are not limited to:

-   -   phenylalanine, tyrosine and tryptophan (amino acids having        aromatic side chains);    -   lysine, arginine and histidine (amino acids having basic side        chains);    -   aspartate and glutamate (amino acids having acidic side chains);    -   asparagine and glutamine (amino acids having amide side chains);        and    -   cysteine and methionine (amino acids having sulphur-containing        side chains). Degrees of identity and similarity can be readily        calculated (Computational Molecular Biology, Lesk, A. M., ed.,        Oxford University Press, New York, 1988; Biocomputing.        Informatics and Genome Projects, Smith, D. W., ed., Academic        Press, New York, 1993; Computer Analysis of Sequence Data, Part        1, Griffin, A. M., and Griffin, H. G., eds., Humana Press, New        Jersey, 1994; Sequence Analysis in Molecular Biology, von        Heinje, G., Academic Press, 1987, Sequence Analysis Primer,        Gribskov, M. and Devereux, J., eds., M Stockton Press, New York,        1991, the BLAST™ software available from NCBI (Altschul, S. F.        et al., 1990, J. Mol. Biol. 215:403-410; Gish, W. &        States, D. J. 1993, Nature Genet. 3:266-272. Madden, T. L. et        al., 1996, Meth. Enzymol. 266:131-141; Altschul, S. F. et al.,        1997, Nucleic Acids Res. 25:3389-3402; Zhang, J. & Madden, T. L.        1997, Genome Res. 7:649-656).

The antibody molecules of the present invention may comprise a completeantibody molecule having full length heavy and light chains or afragment thereof and may be, but are not limited to Fab, modified Fab,Fab′, modified Fab′, F(ab′)2, Fv, single domain antibodies (e.g. VH orVL or VHH), scFv, bi, tri or tetra-valent antibodies, Bis-scFv,diabodies, triabodies, tetrabodies and epitope-binding fragments of anyof the above (see for example Holliger and Hudson, 2005, Nature Biotech.23(9):1126-1136; Adair and Lawson, 2005, Drug Design Reviews—Online2(3), 209-217). The methods for creating and manufacturing theseantibody fragments are well known in the art (see for example Verma etal., 1998, Journal of Immunological Methods, 216, 165-181). Otherantibody fragments for use in the present invention include the Fab andFab′ fragments described in International patent applicationsWO2005/003169, WO2005/003170 and WO2005/003171. Multi-valent antibodiesmay comprise multiple specificities e.g bispecific or may bemonospecific (see for example WO 92/22853, WO05/113605, WO2009/040562and WO2010/035012).

In one embodiment the antibody molecule of the present disclosure is anantibody Fab′ fragment comprising the variable regions shown in SEQ IDNOs: 15 and 29 for example for the light and heavy chain respectively.In one embodiment the antibody molecule has a light chain comprising thesequence given in SEQ ID NO:22 and a heavy chain comprising the sequencegiven in SEQ ID NO:36.

In one embodiment the antibody molecule of the present disclosure is afull length IgG1 antibody comprising the variable regions shown in SEQID NOs: 15 and 29 for example for the light and heavy chainrespectively. In one embodiment the antibody molecule has a light chaincomprising the sequence given in SEQ ID NO:22 and a heavy chaincomprising the sequence given in SEQ ID NO:72.

In one embodiment the antibody molecule of the present disclosure is afull length IgG4 format comprising the variable regions shown in SEQ IDNOs: 15 and 29 for example for the light and heavy chain respectively.In one embodiment the antibody molecule has a light chain comprising thesequence given in SEQ ID NO:22 and a heavy chain comprising the sequencegiven in SEQ ID NO:87.

In one embodiment the antibody molecule of the present disclosure is afull length IgG4P format comprising the variable regions shown in SEQ IDNOs: 15 and 29 for example for the light and heavy chain respectively.In one embodiment the antibody molecule has a light chain comprising thesequence given in SEQ ID NO:22 and a heavy chain comprising the sequencegiven in SEQ ID NO:43.

IgG4P as employed herein is a mutation of the wild-type IgG4 isotypewhere amino acid 241 is replaced by proline see for example where serineat position 241 has been changed to proline as described in Angal etal., Molecular Immunology, 1993, 30 (1), 105-108.

In one embodiment the antibody according to the present disclosure isprovided as FcRn binding antibody fusion protein which comprises animmunoglobulin moiety, for example a Fab or Fab′ fragment, and one ortwo single domain antibodies (dAb) linked directly or indirectlythereto, for example as described in WO2009/040562, WO2010035012,WO2011/030107, WO2011/061492 and WO2011/086091 all incorporated hereinby reference.

In one embodiment the fusion protein comprises two domain antibodies,for example as a variable heavy (VH) and variable light (VL) pairing,optionally linked by a disulphide bond.

In one embodiment the Fab or Fab′ element of the fusion protein has thesame or similar specificity to the single domain antibody or antibodies.In one embodiment the Fab or Fab′ has a different specificity to thesingle domain antibody or antibodies, that is to say the fusion proteinis multivalent. In one embodiment a multivalent fusion protein accordingto the present invention has an albumin binding site, for example aVH/VL pair therein provides an albumin binding site. In one suchembodiment the heavy chain comprises the sequence given in SEQ ID NO:50and the light chain comprises the sequence given in SEQ ID NO:46 or SEQID NO:78. This Fab-dsFv format is illustrated in FIG. 25 herein.

In one embodiment the Fab or Fab′ according to the present disclosure isconjugated to a PEG molecule or human serum albumin.

CA170_01519g57 and 1519 and 1519.g57 are employed inchangeably hereinand are used to refer to a specific pair of antibody variable regionswhich may be used in a number of different formats. These variableregions are the heavy chain sequence given in SEQ ID NO:29 and the lightchain sequence given in SEQ ID NO:15 (FIG. 1 ).

The constant region domains of the antibody molecule of the presentinvention, if present, may be selected having regard to the proposedfunction of the antibody molecule, and in particular the effectorfunctions which may be required. For example, the constant regiondomains may be human IgA, IgD, IgE, IgG or IgM domains. In particular,human IgG constant region domains may be used, especially of the IgG1and IgG3 isotypes when the antibody molecule is intended for therapeuticuses and antibody effector functions are required. Alternatively, IgG2and IgG4 isotypes may be used when the antibody molecule is intended fortherapeutic purposes and antibody effector functions are not required.It will be appreciated that sequence variants of these constant regiondomains may also be used. For example IgG4 molecules in which the serineat position 241 has been changed to proline as described in Angal etal., Molecular Immunology, 1993, 30 (1), 105-108 may be used. It willalso be understood by one skilled in the art that antibodies may undergoa variety of posttranslational modifications. The type and extent ofthese modifications often depends on the host cell line used to expressthe antibody as well as the culture conditions. Such modifications mayinclude variations in glycosylation, methionine oxidation,diketopiperazine formation, aspartate isomerization and asparaginedeamidation. A frequent modification is the loss of a carboxy-terminalbasic residue (such as lysine or arginine) due to the action ofcarboxypeptidases (as described in Harris, R J. Journal ofChromatography 705:129-134, 1995). Accordingly, the C-terminal lysine ofthe antibody heavy chain may be absent.

In one embodiment the antibody heavy chain comprises a CH1 domain andthe antibody light chain comprises a CL domain, either kappa or lambda.

In one embodiment the light chain has the sequence given in SEQ ID NO:22and the heavy chain has the sequence given in SEQ ID NO:43.

In one embodiment the light chain has the sequence given in SEQ ID NO:22and the heavy chain has the sequence given in SEQ ID NO:72.

In one embodiment a C-terminal amino acid from the antibody molecule iscleaved during post-translation modifications.

In one embodiment an N-terminal amino acid from the antibody molecule iscleaved during post-translation modifications.

Also provided by the present invention is a specific region or epitopeof human FcRn which is bound by an antibody provided by the presentinvention, in particular an antibody comprising the heavy chain sequencegH2O (SEQ ID NO:29) and/or the light chain sequence gL20 (SEQ ID NO:15).

This specific region or epitope of the human FcRn polypeptide can beidentified by any suitable epitope mapping method known in the art incombination with any one of the antibodies provided by the presentinvention. Examples of such methods include screening peptides ofvarying lengths derived from FcRn for binding to the antibody of thepresent invention with the smallest fragment that can specifically bindto the antibody containing the sequence of the epitope recognised by theantibody. The FcRn peptides may be produced synthetically or byproteolytic digestion of the FcRn polypeptide. Peptides that bind theantibody can be identified by, for example, mass spectrometric analysis.In another example, NMR spectroscopy or X-ray crystallography can beused to identify the epitope bound by an antibody of the presentinvention. Once identified, the epitopic fragment which binds anantibody of the present invention can be used, if required, as animmunogen to obtain additional antibodies which bind the same epitope.

In one embodiment the antibody of the present disclosure binds the humanFcRn alpha chain extracellular sequence as shown below:

(SEQ ID NO: 94) AESHLSLLYH LTAVSSPAPG TPAFWVSGWL GPQQYLSYNSLRGEAEPCGA WVWENQVSWY WEKETTDLRI KEKLFLEAFKALGGKGPYTL QGLLGCELGP DNTSVPTAKF ALNG EEF MNFDLKQGTWGGD WPEALAISQR WQQQDKAANK ELTFLLFSCPHRLREHLERG RGNLEWKEPP SMRLKARPSS PGFSVLTCSAFSFYPPELQL RFLRNGLAAG TGQGDFGPNS DGSFHASSSLTVKSGDEHHY CCIVQHAGLA QPLRVELESPAKSS.

The residues underlined are those known to be critical for theinteraction of human FcRn with the Fc region of human IgG and thoseresidues highlighted in bold are those involved in the interaction ofFcRn with the 1519 antibody of the present disclosure comprising theheavy chain sequence gH2O (SEQ ID NO:29) and the light chain sequencegL20 (SEQ ID NO:15).

In one example, the present invention provides an anti-FcRn antibodymolecule which binds an epitope of human FcRn which comprises at leastone amino acid selected from the group consisting of residues V105,P106, T107, A108 and K109 of SEQ ID NO:94 and at least one residue, forexample at least 2, 3, 4, 5, 6, 7, 8, 9 or 10 residues selected from thegroup consisting of P100, E115, E116, F117, M118, N119, F120, D121,L122, K123, Q124, G128, G129, D130, W131, P132 and E133 of SEQ ID NO:94.

In one example the epitope of the antibody molecule is determined byX-ray crystallography using the FcRn alpha chain extracellular sequence(SEQ ID NO:94) in complex with 132M.

In one example, the present invention provides an anti-FcRn antibodymolecule which binds an epitope of human FcRn which comprises at leastone amino acid selected from the group consisting of residues V105,P106, T107, A108 and K109 of SEQ ID NO:94 and at least one residue, forexample at least 2, 3, 4, 5, 6, 7, 8, 9 or 10 residues, selected fromthe group consisting of E115, E116, F117, M118, N119, F120, D121, L122,K123 and Q124 of SEQ ID NO:94.

In one example, the present invention provides an anti-FcRn antibodymolecule which binds an epitope of human FcRn which comprises at leasttwo, three, four or five amino acids selected from the group consistingof residues V105, P106, T107, A108 and K109 of SEQ ID NO:94 and at leastone residue selected from the group consisting of E115, E116, F117,M118, N119, F120, D121, L122, K123 and Q124 of SEQ ID NO:94.

In one example, the present invention provides an anti-FcRn antibodymolecule which binds an epitope of human FcRn which comprises at leastone amino acid selected from the group consisting of residues V105,P106, T107, A108 and K109 of SEQ ID NO:94 and at least one residueselected from the group consisting of P100, E115, E116, F117, M118,N119, F120, D121, L122, K123, Q124, G128, G129, D130, W131, P132 andE133 of SEQ ID NO:94.

In one example, the present invention provides an anti-FcRn antibodymolecule which binds an epitope of human FcRn which comprises at leastone amino acid selected from the group consisting of residues V105,P106, T107, A108 and K109 of SEQ ID NO:94 and at least one residueselected from the group consisting of P100, M118, N119, F120, D121,L122, K123, Q124 and G128 of SEQ ID NO:94.

In one example, the present invention provides an anti-FcRn antibodymolecule which binds an epitope of human FcRn which comprises residuesV105, P106, T107, A108 and K109 of SEQ ID NO:94 and at least one residueselected from the group consisting of P100, M118, N119, F120, D121,L122, K123, Q124 and G128 of SEQ ID NO:94.

In one example, the present invention provides an anti-FcRn antibodymolecule which binds an epitope of human FcRn which comprises residuesV105, P106, T107, A108 and K109 of SEQ ID NO:94 and at least one residueselected from the group consisting of P100, E115, E116, F117, M118,N119, F120, D121, L122, K123, Q124, G128, G129, D130, W131, P132 andE133 of SEQ ID NO:94.

In one example, the present invention provides an anti-FcRn antibodymolecule which binds an epitope of human FcRn which comprises residuesP100, V105, P106, T107, A108 and K109 of SEQ ID NO:94 and at least oneresidue selected from the group consisting of E115, E116, F117, M118,N119, F120, D121, L122, K123, Q124, G128, G129, D130, W131, P132 andE133 of SEQ ID NO:94.

In one example ‘at least one residue’ may be 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15 or 16 residues.

In one example the present invention provides an anti-FcRn antibodymolecule which binds an epitope of human FcRn which comprises orconsists of residues 100, 105 to 109, 115 to 124 and 129 to 133 of SEQID NO: 94.

Antibodies which cross-block the binding of an antibody moleculeaccording to the present invention in particular, an antibody moleculecomprising the heavy chain sequence given in SEQ ID NO:29 and the lightchain sequence given in SEQ ID NO:15 may be similarly useful in blockingFcRn activity. Accordingly, the present invention also provides ananti-FcRn antibody molecule, which cross-blocks the binding of any oneof the antibody molecules described herein above to human FcRn and/or iscross-blocked from binding human FcRn by any one of those antibodies. Inone embodiment, such an antibody binds to the same epitope as anantibody described herein above. In another embodiment thecross-blocking neutralising antibody binds to an epitope which bordersand/or overlaps with the epitope bound by an antibody described hereinabove.

Cross-blocking antibodies can be identified using any suitable method inthe art, for example by using competition ELISA or BIAcore assays wherebinding of the cross blocking antibody to human FcRn prevents thebinding of an antibody of the present invention or vice versa. Suchcross blocking assays may use isolated natural or recombinant FcRn or asuitable fusion protein/polypeptide. In one example binding andcross-blocking is measured using recombinant human FcRn extracellulardomain (SEQ ID NO:94). In one example the recombinant human FcRn alphachain extracellular domain is used in a complex with β2 microglobulin(β2M) (SEQ ID NO:95).

In one embodiment there is provided an anti-FcRn antibody molecule whichblocks FcRn binding to IgG and which cross-blocks the binding of anantibody whose heavy chain comprises the sequence given in SEQ ID NO:29and whose light chain comprises the sequence given in SEQ ID NO:15 tohuman FcRn. In one embodiment the cross-blocking antibodies provided bythe present invention inhibit the binding of an antibody comprising theheavy chain sequence given in SEQ ID NO:29 and the light chain sequencegiven in SEQ ID NO:15 by greater than 80%, for example by greater than85%, such as by greater than 90%, in particular by greater than 95%.

Alternatively or in addition, anti-FcRn antibodies according to thisaspect of the invention may be cross-blocked from binding to human FcRnby an antibody comprising the heavy chain sequence given in SEQ ID NO:29and the light chain sequence given in SEQ ID NO:15. Also providedtherefore is an anti-FcRn antibody molecule which blocks FcRn binding toIgG and which is cross-blocked from binding human FcRn by an antibodycomprising the heavy chain sequence given in SEQ ID NO:29 and the lightchain sequence given in SEQ ID NO:15. In one embodiment the anti-FcRnantibodies provided by this aspect of the invention are inhibited frombinding human FcRn by an antibody comprising the heavy chain sequencegiven in SEQ ID NO:29 and the light chain sequence given in SEQ ID NO:15by greater than 80%, for example by greater than 85%, such as by greaterthan 90%, in particular by greater than 95%.

In one embodiment the cross-blocking antibodies provided by the presentinvention are fully human. In one embodiment the cross-blockingantibodies provided by the present invention are humanised. In oneembodiment the cross-blocking antibodies provided by the presentinvention have an affinity for human FcRn of 100 pM or less. In oneembodiment the cross-blocking antibodies provided by the presentinvention have an affinity for human FcRn of 50 pM or less. Affinity canbe measured using the methods described herein below.

Biological molecules, such as antibodies or fragments, contain acidicand/or basic functional groups, thereby giving the molecule a netpositive or negative charge. The amount of overall “observed” chargewill depend on the absolute amino acid sequence of the entity, the localenvironment of the charged groups in the 3D structure and theenvironmental conditions of the molecule. The isoelectric point (pI) isthe pH at which a particular molecule or solvent accessible surfacethereof carries no net electrical charge. In one example, the FcRnantibody and fragments of the invention may be engineered to have anappropriate isoelectric point. This may lead to antibodies and/orfragments with more robust properties, in particular suitable solubilityand/or stability profiles and/or improved purification characteristics.

Thus in one aspect the invention provides a humanised FcRn antibodyengineered to have an isoelectric point different to that of theoriginally identified antibody. The antibody may, for example beengineered by replacing an amino acid residue such as replacing anacidic amino acid residue with one or more basic amino acid residues.Alternatively, basic amino acid residues may be introduced or acidicamino acid residues can be removed. Alternatively, if the molecule hasan unacceptably high pI value acidic residues may be introduced to lowerthe pI, as required. It is important that when manipulating the pI caremust be taken to retain the desirable activity of the antibody orfragment. Thus in one embodiment the engineered antibody or fragment hasthe same or substantially the same activity as the “unmodified” antibodyor fragment.

Programs such as **ExPASY www.expasy.ch/tools/pi_tool.html, andwww.iut-arles.up.univ-mrs.fr/w3bb/d_abim/compo-p.html, may be used topredict the isoelectric point of the antibody or fragment.

The antibody molecules of the present invention suitably have a highbinding affinity, in particular in the nanomolar range. Affinity may bemeasured using any suitable method known in the art, including BIAcore,as described in the Examples herein, using isolated natural orrecombinant FcRn or a suitable fusion protein/polypeptide. In oneexample affinity is measured using recombinant human FcRn extracellulardomain as described in the Examples herein (SEQ ID NO:94). In oneexample affinity is measured using the recombinant human FcRn alphachain extracellular domain (SEQ ID NO:94) in association with (32microglobulin (β2M) (SEQ ID NO:95). Suitably the antibody molecules ofthe present invention have a binding affinity for isolated human FcRn ofabout 1 nM or lower. In one embodiment the antibody molecule of thepresent invention has a binding affinity of about 500 pM or lower (i.e.higher affinity). In one embodiment the antibody molecule of the presentinvention has a binding affinity of about 250 pM or lower. In oneembodiment the antibody molecule of the present invention has a bindingaffinity of about 200 pM or lower. In one embodiment the presentinvention provides an anti-FcRn antibody with a binding affinity ofabout 100 pM or lower. In one embodiment the present invention providesa humanised anti-FcRn antibody with a binding affinity of about 100 pMor lower. In one embodiment the present invention provides an anti-FcRnantibody with a binding affinity of 50 pM or lower.

Importantly the antibodies of the present invention are able to bindhuman FcRn at both pH6 and pH7.4 with comparable binding affinity.Advantageously therefore the antibodies are able to continue to bindFcRn even within the endosome, thereby maximising the blocking of FcRnbinding to IgG, see FIG. 10 for an illustration of the mechanism.

In one embodiment the present invention provides an anti-FcRn antibodywith a binding affinity of 100 pM or lower when measured at pH6 andpH7.4.

The affinity of an antibody or binding fragment of the presentinvention, as well as the extent to which a binding agent (such as anantibody) inhibits binding, can be determined by one of ordinary skillin the art using conventional techniques, for example those described byScatchard et al. (Ann. KY. Acad. Sci. 51:660-672 (1949)) or by surfaceplasmon resonance (SPR) using systems such as BIAcore. For surfaceplasmon resonance, target molecules are immobilized on a solid phase andexposed to ligands in a mobile phase running along a flow cell. Ifligand binding to the immobilized target occurs, the local refractiveindex changes, leading to a change in SPR angle, which can be monitoredin real time by detecting changes in the intensity of the reflectedlight. The rates of change of the SPR signal can be analyzed to yieldapparent rate constants for the association and dissociation phases ofthe binding reaction. The ratio of these values gives the apparentequilibrium constant (affinity) (see, e.g., Wolff et al, Cancer Res.53:2560-65 (1993)).

In the present invention affinity of the test antibody molecule istypically determined using SPR as follows. The test antibody molecule iscaptured on the solid phase and human FcRn alpha chain extracellulardomain in non-covalent complex with (32M is run over the capturedantibody in the mobile phase and affinity of the test antibody moleculefor human FcRn determined. The test antibody molecule may be captured onthe solid phase chip surface using any appropriate method, for exampleusing an anti-Fc or anti Fab′ specific capture agent. In one example theaffinity is determined at pH6. In one example the affinity is determinedat pH7.4.

It will be appreciated that the affinity of antibodies provided by thepresent invention may be altered using any suitable method known in theart. The present invention therefore also relates to variants of theantibody molecules of the present invention, which have an improvedaffinity for FcRn. Such variants can be obtained by a number of affinitymaturation protocols including mutating the CDRs (Yang et al., J. Mol.Biol., 254, 392-403, 1995), chain shuffling (Marks et al.,Bio/Technology, 10, 779-783, 1992), use of mutator strains of E. coli(Low et al., J. Mol. Biol., 250, 359-368, 1996), DNA shuffling (Pattenet al., Curr. Opin. Biotechnol., 8, 724-733, 1997), phage display(Thompson et al., J. Mol. Biol., 256, 77-88, 1996) and sexual PCR(Crameri et al., Nature, 391, 288-291, 1998). Vaughan et al. (supra)discusses these methods of affinity maturation.

In one embodiment the antibody molecules of the present invention blockhuman FcRn activity. Assays suitable for determining the ability of anantibody to block FcRn are described in the Examples herein. Suitableassays for determining whether antibodies block FcRn interaction withcirculating IgG molecules as described in the Examples herein. Asuitable assay for determining the ability of an antibody molecule toblock IgG recycling in vitro is described herein below.

If desired an antibody for use in the present invention may beconjugated to one or more effector molecule(s). It will be appreciatedthat the effector molecule may comprise a single effector molecule ortwo or more such molecules so linked as to form a single moiety that canbe attached to the antibodies of the present invention. Where it isdesired to obtain an antibody fragment linked to an effector molecule,this may be prepared by standard chemical or recombinant DNA proceduresin which the antibody fragment is linked either directly or via acoupling agent to the effector molecule. Techniques for conjugating sucheffector molecules to antibodies are well known in the art (see,Hellstrom et al., Controlled Drug Delivery, 2nd Ed., Robinson et al.,eds., 1987, pp. 623-53; Thorpe et al., 1982, Immunol. Rev., 62:119-58and Dubowchik et al., 1999, Pharmacology and Therapeutics, 83, 67-123).Particular chemical procedures include, for example, those described inWO 93/06231, WO 92/22583, WO 89/00195, WO 89/01476 and WO 03/031581.Alternatively, where the effector molecule is a protein or polypeptidethe linkage may be achieved using recombinant DNA procedures, forexample as described in WO 86/01533 and EP0392745.

The term effector molecule as used herein includes, for example,antineoplastic agents, drugs, toxins, biologically active proteins, forexample enzymes, other antibody or antibody fragments, synthetic ornaturally occurring polymers, nucleic acids and fragments thereof e.g.DNA, RNA and fragments thereof, radionuclides, particularly radioiodide,radioisotopes, chelated metals, nanoparticles and reporter groups suchas fluorescent compounds or compounds which may be detected by NMR orESR spectroscopy.

Examples of effector molecules may include cytotoxins or cytotoxicagents including any agent that is detrimental to (e.g. kills) cells.Examples include combrestatins, dolastatins, epothilones, staurosporin,maytansinoids, spongistatins, rhizoxin, halichondrins, roridins,hemiasterlins, taxol, cytochalasin B, gramicidin D, ethidium bromide,emetine, mitomycin, etoposide, tenoposide, vincristine, vinblastine,colchicin, doxorubicin, daunorubicin, dihydroxy anthracin dione,mitoxantrone, mithramycin, actinomycin D, 1-dehydrotestosterone,glucocorticoids, procaine, tetracaine, lidocaine, propranolol, andpuromycin and analogs or homologs thereof.

Effector molecules also include, but are not limited to, antimetabolites(e.g. methotrexate, 6-mercaptopurine, 6-thioguanine, cytarabine,5-fluorouracil decarbazine), alkylating agents (e.g. mechlorethamine,thioepa chlorambucil, melphalan, carmustine (BSNU) and lomustine (CCNU),cyclothosphamide, busulfan, dibromomannitol, streptozotocin, mitomycinC, and cis-dichlorodiamine platinum (II) (DDP) cisplatin),anthracyclines (e.g. daunorubicin (formerly daunomycin) anddoxorubicin), antibiotics (e.g. dactinomycin (formerly actinomycin),bleomycin, mithramycin, anthramycin (AMC), calicheamicins orduocarmycins), and anti-mitotic agents (e.g. vincristine andvinblastine).

Other effector molecules may include chelated radionuclides such as¹¹¹In and ⁹⁰Y, Lu¹⁷⁷, Bismuth²¹³, Californium²⁵², Iridium¹⁹² andTungsten¹⁸⁸/Rhenium¹⁸⁸; or drugs such as but not limited to,alkylphosphocholines, topoisomerase I inhibitors, taxoids and suramin.

Other effector molecules include proteins, peptides and enzymes. Enzymesof interest include, but are not limited to, proteolytic enzymes,hydrolases, lyases, isomerases, transferases. Proteins, polypeptides andpeptides of interest include, but are not limited to, immunoglobulins,toxins such as abrin, ricin A, pseudomonas exotoxin, or diphtheriatoxin, a protein such as insulin, tumour necrosis factor, α-interferon,β-interferon, nerve growth factor, platelet derived growth factor ortissue plasminogen activator, a thrombotic agent or an anti-angiogenicagent, e.g. angiostatin or endostatin, or, a biological responsemodifier such as a lymphokine, interleukin-1 (IL-1), interleukin-2(IL-2), granulocyte macrophage colony stimulating factor (GM-CSF),granulocyte colony stimulating factor (G-CSF), nerve growth factor (NGF)or other growth factor and immunoglobulins.

Other effector molecules may include detectable substances useful forexample in diagnosis. Examples of detectable substances include variousenzymes, prosthetic groups, fluorescent materials, luminescentmaterials, bioluminescent materials, radioactive nuclides, positronemitting metals (for use in positron emission tomography), andnonradioactive paramagnetic metal ions. See generally U.S. Pat. No.4,741,900 for metal ions which can be conjugated to antibodies for useas diagnostics. Suitable enzymes include horseradish peroxidase,alkaline phosphatase, beta-galactosidase, or acetylcholinesterase;suitable prosthetic groups include streptavidin, avidin and biotin;suitable fluorescent materials include umbelliferone, fluorescein,fluorescein isothiocyanate, rhodamine, dichlorotriazinylaminefluorescein, dansyl chloride and phycoerythrin; suitable luminescentmaterials include luminol; suitable bioluminescent materials includeluciferase, luciferin, and aequorin; and suitable radioactive nuclidesinclude ¹²⁵I, ¹³¹I, ¹¹¹In and ⁹⁹Tc.

In another example the effector molecule may increase the half-life ofthe antibody in vivo, and/or reduce immunogenicity of the antibodyand/or enhance the delivery of an antibody across an epithelial barrierto the immune system. Examples of suitable effector molecules of thistype include polymers, albumin, albumin binding proteins or albuminbinding compounds such as those described in WO05/117984.

In one embodiment a half-life provided by an effector molecule which isindependent of FcRn is advantageous.

Where the effector molecule is a polymer it may, in general, be asynthetic or a naturally occurring polymer, for example an optionallysubstituted straight or branched chain polyalkylene, polyalkenylene orpolyoxyalkylene polymer or a branched or unbranched polysaccharide, e.g.a homo- or hetero-polysaccharide.

Specific optional substituents which may be present on theabove-mentioned synthetic polymers include one or more hydroxy, methylor methoxy groups.

Specific examples of synthetic polymers include optionally substitutedstraight or branched chain poly(ethyleneglycol), poly(propyleneglycol)poly(vinylalcohol) or derivatives thereof, especially optionallysubstituted poly(ethyleneglycol) such as methoxypoly(ethyleneglycol) orderivatives thereof.

Specific naturally occurring polymers include lactose, amylose, dextran,glycogen or derivatives thereof.

In one embodiment the polymer is albumin or a fragment thereof, such ashuman serum albumin or a fragment thereof.

“Derivatives” as used herein is intended to include reactivederivatives, for example thiol-selective reactive groups such asmaleimides and the like. The reactive group may be linked directly orthrough a linker segment to the polymer. It will be appreciated that theresidue of such a group will in some instances form part of the productas the linking group between the antibody fragment and the polymer.

The size of the polymer may be varied as desired, but will generally bein an average molecular weight range from 500 Da to 50000 Da, forexample from 5000 to 40000 Da such as from 20000 to 40000 Da. Thepolymer size may in particular be selected on the basis of the intendeduse of the product for example ability to localize to certain tissuessuch as tumors or extend circulating half-life (for review see Chapman,2002, Advanced Drug Delivery Reviews, 54, 531-545). Thus, for example,where the product is intended to leave the circulation and penetratetissue, for example for use in the treatment of a tumour, it may beadvantageous to use a small molecular weight polymer, for example with amolecular weight of around 5000 Da. For applications where the productremains in the circulation, it may be advantageous to use a highermolecular weight polymer, for example having a molecular weight in therange from 20000 Da to 40000 Da.

Suitable polymers include a polyalkylene polymer, such as apoly(ethyleneglycol) or, especially, a methoxypoly(ethyleneglycol) or aderivative thereof, and especially with a molecular weight in the rangefrom about 15000 Da to about 40000 Da.

In one example antibodies for use in the present invention are attachedto poly(ethyleneglycol) (PEG) moieties. In one particular example theantibody is an antibody fragment and the PEG molecules may be attachedthrough any available amino acid side-chain or terminal amino acidfunctional group located in the antibody fragment, for example any freeamino, imino, thiol, hydroxyl or carboxyl group. Such amino acids mayoccur naturally in the antibody fragment or may be engineered into thefragment using recombinant DNA methods (see for example U.S. Pat. Nos.5,219,996; 5,667,425; WO98/25971, WO2008/038024). In one example theantibody molecule of the present invention is a modified Fab fragmentwherein the modification is the addition to the C-terminal end of itsheavy chain one or more amino acids to allow the attachment of aneffector molecule. Suitably, the additional amino acids form a modifiedhinge region containing one or more cysteine residues to which theeffector molecule may be attached. Multiple sites can be used to attachtwo or more PEG molecules.

Suitably PEG molecules are covalently linked through a thiol group of atleast one cysteine residue located in the antibody fragment. Eachpolymer molecule attached to the modified antibody fragment may becovalently linked to the sulphur atom of a cysteine residue located inthe fragment. The covalent linkage will generally be a disulphide bondor, in particular, a sulphur-carbon bond. Where a thiol group is used asthe point of attachment appropriately activated effector molecules, forexample thiol selective derivatives such as maleimides and cysteinederivatives may be used. An activated polymer may be used as thestarting material in the preparation of polymer-modified antibodyfragments as described above. The activated polymer may be any polymercontaining a thiol reactive group such as an α-halocarboxylic acid orester, e.g. iodoacetamide, an imide, e.g. maleimide, a vinyl sulphone ora disulphide. Such starting materials may be obtained commercially (forexample from Nektar, formerly Shearwater Polymers Inc., Huntsville,Ala., USA) or may be prepared from commercially available startingmaterials using conventional chemical procedures. Particular PEGmolecules include 20K methoxy-PEG-amine (obtainable from Nektar,formerly Shearwater; Rapp Polymere; and SunBio) and M-PEG-SPA(obtainable from Nektar, formerly Shearwater).

In one embodiment, the antibody is a modified Fab fragment, Fab′fragment or diFab which is PEGylated, i.e. has PEG(poly(ethyleneglycol)) covalently attached thereto, e.g. according tothe method disclosed in EP 0948544 or EP1090037 [see also“Poly(ethyleneglycol) Chemistry, Biotechnical and BiomedicalApplications”, 1992, J. Milton Harris (ed), Plenum Press, New York,“Poly(ethyleneglycol) Chemistry and Biological Applications”, 1997, J.Milton Harris and S. Zalipsky (eds), American Chemical Society,Washington D.C. and “Bioconjugation Protein Coupling Techniques for theBiomedical Sciences”, 1998, M. Aslam and A. Dent, Grove Publishers, NewYork; Chapman, A. 2002, Advanced Drug Delivery Reviews 2002,54:531-545]. In one example PEG is attached to a cysteine in the hingeregion. In one example, a PEG modified Fab fragment has a maleimidegroup covalently linked to a single thiol group in a modified hingeregion. A lysine residue may be covalently linked to the maleimide groupand to each of the amine groups on the lysine residue may be attached amethoxypoly(ethyleneglycol) polymer having a molecular weight ofapproximately 20,000 Da. The total molecular weight of the PEG attachedto the Fab fragment may therefore be approximately 40,000 Da.

Particular PEG molecules include 243-(N-maleimido)propionamidolethylamide of N,N′-bis(methoxypoly(ethylene glycol) MW 20,000) modifiedlysine, also known as PEG2MAL40K (obtainable from Nektar, formerlyShearwater).

Alternative sources of PEG linkers include NOF who supply GL2-400MA3(wherein m in the structure below is 5) and GL2-400MA (where m is 2) andn is approximately 450:

That is to say each PEG is about 20,000 Da.

Thus in one embodiment the PEG is2,3-Bis(methylpolyoxyethylene-oxy)-1-{[3-(6-maleimido-1-oxohexyl)amino]propyloxy}hexane (the 2 arm branched PEG, —CH₂)₃NHCO(CH₂)₅-MAL, Mw 40,000 known asSUNBRIGHT GL2-400MA3.

Further alternative PEG effector molecules of the following type:

are available from Dr Reddy, NOF and Jenkem.

In one embodiment there is provided an antibody which is PEGylated (forexample with a PEG described herein), attached through a cysteine aminoacid residue at or about amino acid 226 in the chain, for example aminoacid 226 of the heavy chain (by sequential numbering), for example aminoacid 226 of SEQ ID NO:36.

In one embodiment the present disclosure provides a Fab′PEG moleculecomprising one or more PEG polymers, for example 1 or 2 polymers such asa 40 kDa polymer or polymers.

Fab′-PEG molecules according to the present disclosure may beparticularly advantageous in that they have a half-life independent ofthe Fc fragment. In one example the present invention provides a methodtreating a disease ameliorated by blocking human FcRn comprisingadministering a therapeutically effective amount of an anti-FcRnantibody or binding fragment thereof wherein the antibody or bindingfragment thereof has a half life that is independent of Fc binding toFcRn.

In one embodiment there is provided a Fab′ conjugated to a polymer, suchas a PEG molecule, a starch molecule or an albumin molecule.

In one embodiment there is provided a scFv conjugated to a polymer, suchas a PEG molecule, a starch molecule or an albumin molecule.

In one embodiment the antibody or fragment is conjugated to a starchmolecule, for example to increase the half life. Methods of conjugatingstarch to a protein as described in U.S. Pat. No. 8,017,739 incorporatedherein by reference.

In one embodiment there is provided an anti-FcRn binding molecule which:

-   -   Causes 70% reduction of plasma IgG concentration,    -   With not more than 20% reduction of plasma albumin        concentration, and/or    -   With the possibility of repeat dosing to achieve long-term        maintenance of low plasma IgG concentration.

The present invention also provides an isolated DNA sequence encodingthe heavy and/or light chain(s) of an antibody molecule of the presentinvention. Suitably, the DNA sequence encodes the heavy or the lightchain of an antibody molecule of the present invention. The DNA sequenceof the present invention may comprise synthetic DNA, for instanceproduced by chemical processing, cDNA, genomic DNA or any combinationthereof.

DNA sequences which encode an antibody molecule of the present inventioncan be obtained by methods well known to those skilled in the art. Forexample, DNA sequences coding for part or all of the antibody heavy andlight chains may be synthesised as desired from the determined DNAsequences or on the basis of the corresponding amino acid sequences.

DNA coding for acceptor framework sequences is widely available to thoseskilled in the art and can be readily synthesised on the basis of theirknown amino acid sequences.

Standard techniques of molecular biology may be used to prepare DNAsequences coding for the antibody molecule of the present invention.Desired DNA sequences may be synthesised completely or in part usingoligonucleotide synthesis techniques. Site-directed mutagenesis andpolymerase chain reaction (PCR) techniques may be used as appropriate.

Examples of suitable DNA sequences are provided in herein.

Examples of suitable DNA sequences encoding the 1519 light chainvariable region are provided in SEQ ID NO:16, SEQ ID NO:17 and SEQ IDNO:90. Examples of suitable DNA sequences encoding the 1519 heavy chainvariable region are provided in SEQ ID NO:30, SEQ ID NO:31 and SEQ IDNO:92.

Examples of suitable DNA sequences encoding the 1519 light chain(variable and constant) are provided in SEQ ID NO:23, SEQ ID NO:75 andSEQ ID NO:91.

Examples of suitable DNA sequences encoding the 1519 heavy chain(variable and constant, depending on format) are provided in SEQ IDNOs:37, 38 and 76 (Fab′), SEQ ID NO:72 or 85 (IgG1), SEQ ID NO: 44 or 93(IgG4P) and SEQ ID:88 (IgG4).

Accordingly in one example the present invention provides an isolatedDNA sequence encoding the heavy chain of an antibody Fab′ fragment ofthe present invention which comprises the sequence given in SEQ IDNO:37. Also provided is an isolated DNA sequence encoding the lightchain of an antibody Fab′ fragment of the present invention whichcomprises the sequence given in SEQ ID NO:23.

In one example the present invention provides an isolated DNA sequenceencoding the heavy chain and the light chain of an IgG4(P) antibody ofthe present invention in which the DNA encoding the heavy chaincomprises the sequence given in SEQ ID NO:44 or SEQ ID NO:93 and the DNAencoding the light chain comprises the sequence given in SEQ ID NO:75 orSEQ ID NO:91.

In one example the present invention provides an isolated DNA sequenceencoding the heavy chain and the light chain of a Fab-dsFv antibody ofthe present invention in which the DNA encoding the heavy chaincomprises the sequence given in SEQ ID NO:51 or SEQ ID NO:80 and the DNAencoding the light chain comprises the sequence given in SEQ ID NO:47 orSEQ ID NO:79.

The present invention also relates to a cloning or expression vectorcomprising one or more DNA sequences of the present invention.Accordingly, provided is a cloning or expression vector comprising oneor more DNA sequences encoding an antibody of the present invention.Suitably, the cloning or expression vector comprises two DNA sequences,encoding the light chain and the heavy chain of the antibody molecule ofthe present invention, respectively and suitable signal sequences. Inone example the vector comprises an intergenic sequence between theheavy and the light chains (see WO03/048208).

General methods by which the vectors may be constructed, transfectionmethods and culture methods are well known to those skilled in the art.In this respect, reference is made to “Current Protocols in MolecularBiology”, 1999, F. M. Ausubel (ed), Wiley Interscience, New York and theManiatis Manual produced by Cold Spring Harbor Publishing.

Also provided is a host cell comprising one or more cloning orexpression vectors comprising one or more DNA sequences encoding anantibody of the present invention. Any suitable host cell/vector systemmay be used for expression of the DNA sequences encoding the antibodymolecule of the present invention. Bacterial, for example E. coli, andother microbial systems may be used or eukaryotic, for examplemammalian, host cell expression systems may also be used. Suitablemammalian host cells include CHO, myeloma or hybridoma cells.

Suitable types of Chinese Hamster Ovary (CHO cells) for use in thepresent invention may include CHO and CHO-K1 cells including dhfr-CHOcells, such as CHO-DG44 cells and CHO-DXB11 cells and which may be usedwith a DHFR selectable marker or CHOK1-SV cells which may be used with aglutamine synthetase selectable marker. Other cell types of use inexpressing antibodies include lymphocytic cell lines, e.g., NSO myelomacells and SP2 cells, COS cells.

The present invention also provides a process for the production of anantibody molecule according to the present invention comprisingculturing a host cell containing a vector of the present invention underconditions suitable for leading to expression of protein from DNAencoding the antibody molecule of the present invention, and isolatingthe antibody molecule.

The antibody molecule may comprise only a heavy or light chainpolypeptide, in which case only a heavy chain or light chain polypeptidecoding sequence needs to be used to transfect the host cells. Forproduction of products comprising both heavy and light chains, the cellline may be transfected with two vectors, a first vector encoding alight chain polypeptide and a second vector encoding a heavy chainpolypeptide. Alternatively, a single vector may be used, the vectorincluding sequences encoding light chain and heavy chain polypeptides.

The antibodies and fragments according to the present disclosure areexpressed at good levels from host cells. Thus the properties of theantibodies and/or fragments are conducive to commercial processing.

Thus there is a provided a process for culturing a host cell andexpressing an antibody or fragment thereof, isolating the latter andoptionally purifying the same to provide an isolated antibody orfragment. In one embodiment the process further comprises the step ofconjugating an effector molecule to the isolated antibody or fragment,for example conjugating to a PEG polymer in particular as describedherein.

In one embodiment there is provided a process for purifying an antibody(in particular an antibody or fragment according to the invention)comprising the steps: performing anion exchange chromatography innon-binding mode such that the impurities are retained on the column andthe antibody is eluted.

In one embodiment the purification employs affinity capture on an FcRncolumn.

In one embodiment the purification employs carbicron blue or similar forpurification of albumin fusion or conjugate molecules.

Suitable ion exchange resins for use in the process include Q.FF resin(supplied by GE-Healthcare). The step may, for example be performed at apH about 8.

The process may further comprise an initial capture step employingcation exchange chromatography, performed for example at a pH of about 4to 5, such as 4.5. The cation exchange chromatography may, for exampleemploy a resin such as CaptoS resin or SP sepharose FF (supplied byGE-Healthcare). The antibody or fragment can then be eluted from theresin employing an ionic salt solution such as sodium chloride, forexample at a concentration of 200 mM.

Thus the chromatograph step or steps may include one or more washingsteps, as appropriate.

The purification process may also comprise one or more filtration steps,such as a diafiltration step.

Thus in one embodiment there is provided a purified anti-FcRn antibodyor fragment, for example a humanised antibody or fragment, in particularan antibody or fragment according to the invention, in substantiallypurified from, in particular free or substantially free of endotoxinand/or host cell protein or DNA.

Purified form as used supra is intended to refer to at least 90% purity,such as 91, 92, 93, 94, 95, 96, 97, 98, 99% w/w or more pure.

Substantially free of endotoxin is generally intended to refer to anendotoxin content of 1 EU per mg antibody product or less such as 0.5 or0.1 EU per mg product.

Substantially free of host cell protein or DNA is generally intended torefer to host cell protein and/or DNA content 400 μg per mg of antibodyproduct or less such as 100 μg per mg or less, in particular 20 μg permg, as appropriate.

The antibody molecule of the present invention may also be used indiagnosis, for example in the in vivo diagnosis and imaging of diseasestates involving FcRn.

As the antibodies of the present invention are useful in the treatmentand/or prophylaxis of a pathological condition, the present inventionalso provides a pharmaceutical or diagnostic composition comprising anantibody molecule of the present invention in combination with one ormore of a pharmaceutically acceptable excipient, diluent or carrier.Accordingly, provided is the use of an antibody molecule of theinvention for the manufacture of a medicament. The composition willusually be supplied as part of a sterile, pharmaceutical compositionthat will normally include a pharmaceutically acceptable carrier. Apharmaceutical composition of the present invention may additionallycomprise a pharmaceutically-acceptable excipient.

The present invention also provides a process for preparation of apharmaceutical or diagnostic composition comprising adding and mixingthe antibody molecule of the present invention together with one or moreof a pharmaceutically acceptable excipient, diluent or carrier.

The antibody molecule may be the sole active ingredient in thepharmaceutical or diagnostic composition or may be accompanied by otheractive ingredients including other antibody ingredients or non-antibodyingredients such as steroids or other drug molecules, in particular drugmolecules whose half-life is independent of FcRn binding.

The pharmaceutical compositions suitably comprise a therapeuticallyeffective amount of the antibody of the invention. The term“therapeutically effective amount” as used herein refers to an amount ofa therapeutic agent needed to treat, ameliorate or prevent a targeteddisease or condition, or to exhibit a detectable therapeutic orpreventative effect. For any antibody, the therapeutically effectiveamount can be estimated initially either in cell culture assays or inanimal models, usually in rodents, rabbits, dogs, pigs or primates. Theanimal model may also be used to determine the appropriate concentrationrange and route of administration. Such information can then be used todetermine useful doses and routes for administration in humans.

The precise therapeutically effective amount for a human subject willdepend upon the severity of the disease state, the general health of thesubject, the age, weight and gender of the subject, diet, time andfrequency of administration, drug combination(s), reaction sensitivitiesand tolerance/response to therapy. This amount can be determined byroutine experimentation and is within the judgement of the clinician.Generally, a therapeutically effective amount will be from 0.01 mg/kg to500 mg/kg, for example 0.1 mg/kg to 200 mg/kg, such as 100 mg/Kg.Pharmaceutical compositions may be conveniently presented in unit doseforms containing a predetermined amount of an active agent of theinvention per dose.

Therapeutic doses of the antibodies according to the present disclosureshow no apparent toxicology effects in vivo.

In one embodiment of an antibody or fragment according to the inventiona single dose may provide up to a 70% reduction in circulating IgGlevels.

The maximal therapeutic reduction in circulating IgG may be observedabout 1 week after administration of the relevant therapeutic dose. Thelevels of IgG may recover over about a six week period if furthertherapeutic doses are not delivered.

Advantageously, the levels of IgG in vivo may be maintained at anappropriately low level by administration of sequential doses of theantibody or fragments according to the disclosure.

Compositions may be administered individually to a patient or may beadministered in combination (e.g. simultaneously, sequentially orseparately) with other agents, drugs or hormones.

In one embodiment the antibodies or fragments according to the presentdisclosure are employed with an immunosuppressant therapy, such as asteroid, in particular prednisone.

In one embodiment the antibodies or fragments according to the presentdisclosure are employed with Rituximab or other B cell therapies.

In one embodiment the antibodies or fragments according to the presentdisclosure are employed with any B cell or T cell modulating agent orimmunomodulator. Examples include methotrexate, microphenyolate andazathioprine.

The dose at which the antibody molecule of the present invention isadministered depends on the nature of the condition to be treated, theextent of the inflammation present and on whether the antibody moleculeis being used prophylactically or to treat an existing condition.

The frequency of dose will depend on the half-life of the antibodymolecule and the duration of its effect. If the antibody molecule has ashort half-life (e.g. 2 to 10 hours) it may be necessary to give one ormore doses per day. Alternatively, if the antibody molecule has a longhalf life (e.g. 2 to 15 days) and/or long lasting pharmacodynamics (PD)profile it may only be necessary to give a dosage once per day, once perweek or even once every 1 or 2 months.

In one embodiment the dose is delivered bi-weekly, i.e. twice a month.

Half life as employed herein is intended to refer to the duration of themolecule in circulation, for example in serum/plasma.

Pharmacodynamics as employed herein refers to the profile and inparticular duration of the biological action of the molecule accordingthe present disclosure.

The pharmaceutically acceptable carrier should not itself induce theproduction of antibodies harmful to the individual receiving thecomposition and should not be toxic. Suitable carriers may be large,slowly metabolised macromolecules such as proteins, polypeptides,liposomes, polysaccharides, polylactic acids, polyglycolic acids,polymeric amino acids, amino acid copolymers and inactive virusparticles.

Pharmaceutically acceptable salts can be used, for example mineral acidsalts, such as hydrochlorides, hydrobromides, phosphates and sulphates,or salts of organic acids, such as acetates, propionates, malonates andbenzoates.

Pharmaceutically acceptable carriers in therapeutic compositions mayadditionally contain liquids such as water, saline, glycerol andethanol. Additionally, auxiliary substances, such as wetting oremulsifying agents or pH buffering substances, may be present in suchcompositions. Such carriers enable the pharmaceutical compositions to beformulated as tablets, pills, dragees, capsules, liquids, gels, syrups,slurries and suspensions, for ingestion by the patient.

Suitable forms for administration include forms suitable for parenteraladministration, e.g. by injection or infusion, for example by bolusinjection or continuous infusion. Where the product is for injection orinfusion, it may take the form of a suspension, solution or emulsion inan oily or aqueous vehicle and it may contain formulatory agents, suchas suspending, preservative, stabilising and/or dispersing agents.Alternatively, the antibody molecule may be in dry form, forreconstitution before use with an appropriate sterile liquid.

Once formulated, the compositions of the invention can be administereddirectly to the subject. The subjects to be treated can be animals.However, in one or more embodiments the compositions are adapted foradministration to human subjects.

Suitably in formulations according to the present disclosure, the pH ofthe final formulation is not similar to the value of the isoelectricpoint of the antibody or fragment, for example if the pI of the proteinis in the range 8-9 or above then a formulation pH of 7 may beappropriate. Whilst not wishing to be bound by theory it is thought thatthis may ultimately provide a final formulation with improved stability,for example the antibody or fragment remains in solution.

In one example the pharmaceutical formulation at a pH in the range of4.0 to 7.0 comprises: 1 to 200 mg/mL of an antibody molecule accordingto the present disclosure, 1 to 100 mM of a buffer, 0.001 to 1% of asurfactant, a) 10 to 500 mM of a stabiliser, b) 10 to 500 mM of astabiliser and 5 to 500 mM of a tonicity agent, or c) 5 to 500 mM of atonicity agent.

The pharmaceutical compositions of this invention may be administered byany number of routes including, but not limited to, oral, intravenous,intramuscular, intra-arterial, intramedullary, intrathecal,intraventricular, transdermal, transcutaneous (for example, seeWO98/20734), subcutaneous, intraperitoneal, intranasal, enteral,topical, sublingual, intravaginal or rectal routes. Hyposprays may alsobe used to administer the pharmaceutical compositions of the invention.Typically, the therapeutic compositions may be prepared as injectables,either as liquid solutions or suspensions. Solid forms suitable forsolution in, or suspension in, liquid vehicles prior to injection mayalso be prepared.

Direct delivery of the compositions will generally be accomplished byinjection, subcutaneously, intraperitoneally, intravenously orintramuscularly, or delivered to the interstitial space of a tissue. Thecompositions can also be administered into a lesion. Dosage treatmentmay be a single dose schedule or a multiple dose schedule.

It will be appreciated that the active ingredient in the compositionwill be an antibody molecule. As such, it will be susceptible todegradation in the gastrointestinal tract. Thus, if the composition isto be administered by a route using the gastrointestinal tract, thecomposition will need to contain agents which protect the antibody fromdegradation but which release the antibody once it has been absorbedfrom the gastrointestinal tract.

A thorough discussion of pharmaceutically acceptable carriers isavailable in Remington's Pharmaceutical Sciences (Mack PublishingCompany, N.J. 1991).

In one embodiment the formulation is provided as a formulation fortopical administrations including inhalation.

Suitable inhalable preparations include inhalable powders, meteringaerosols containing propellant gases or inhalable solutions free frompropellant gases. Inhalable powders according to the disclosurecontaining the active substance may consist solely of the abovementionedactive substances or of a mixture of the abovementioned activesubstances with physiologically acceptable excipient.

These inhalable powders may include monosaccharides (e.g. glucose orarabinose), disaccharides (e.g. lactose, saccharose, maltose), oligo-and polysaccharides (e.g. dextranes), polyalcohols (e.g. sorbitol,mannitol, xylitol), salts (e.g. sodium chloride, calcium carbonate) ormixtures of these with one another. Mono- or disaccharides are suitablyused, the use of lactose or glucose, particularly but not exclusively inthe form of their hydrates.

Particles for deposition in the lung require a particle size less than10 microns, such as 1-9 microns for example from 1 to 5 μm. The particlesize of the active ingredient (such as the antibody or fragment) is ofprimary importance.

The propellent gases which can be used to prepare the inhalable aerosolsare known in the art. Suitable propellent gases are selected from amonghydrocarbons such as n-propane, n-butane or isobutane andhalohydrocarbons such as chlorinated and/or fluorinated derivatives ofmethane, ethane, propane, butane, cyclopropane or cyclobutane. Theabovementioned propellent gases may be used on their own or in mixturesthereof.

Particularly suitable propellent gases are halogenated alkanederivatives selected from among TG 11, TG 12, TG 134a and TG227. Of theabovementioned halogenated hydrocarbons, TG134a(1,1,1,2-tetrafluoroethane) and TG227 (1,1,1,2,3,3,3-heptafluoropropane)and mixtures thereof are particularly suitable.

The propellent-gas-containing inhalable aerosols may also contain otheringredients such as cosolvents, stabilisers, surface-active agents(surfactants), antioxidants, lubricants and means for adjusting the pH.All these ingredients are known in the art.

The propellant-gas-containing inhalable aerosols according to theinvention may contain up to 5% by weight of active substance. Aerosolsaccording to the invention contain, for example, 0.002 to 5% by weight,0.01 to 3% by weight, 0.015 to 2% by weight, 0.1 to 2% by weight, 0.5 to2% by weight or 0.5 to 1% by weight of active ingredient.

Alternatively topical administrations to the lung may also be byadministration of a liquid solution or suspension formulation, forexample employing a device such as a nebulizer, for example, a nebulizerconnected to a compressor (e.g., the Pari LC-Jet Plus® nebulizerconnected to a Pari Master® compressor manufactured by Pari RespiratoryEquipment, Inc., Richmond, Va.).

The antibody of the invention can be delivered dispersed in a solvent,e.g., in the form of a solution or a suspension. It can be suspended inan appropriate physiological solution, e.g., saline or otherpharmacologically acceptable solvent or a buffered solution. Bufferedsolutions known in the art may contain 0.05 mg to 0.15 mg disodiumedetate, 8.0 mg to 9.0 mg NaCl, 0.15 mg to 0.25 mg polysorbate, 0.25 mgto 0.30 mg anhydrous citric acid, and 0.45 mg to 0.55 mg sodium citrateper 1 ml of water so as to achieve a pH of about 4.0 to 5.0. Asuspension can employ, for example, lyophilised antibody.

The therapeutic suspensions or solution formulations can also containone or more excipients. Excipients are well known in the art and includebuffers (e.g., citrate buffer, phosphate buffer, acetate buffer andbicarbonate buffer), amino acids, urea, alcohols, ascorbic acid,phospholipids, proteins (e.g., serum albumin), EDTA, sodium chloride,liposomes, mannitol, sorbitol, and glycerol. Solutions or suspensionscan be encapsulated in liposomes or biodegradable microspheres. Theformulation will generally be provided in a substantially sterile formemploying sterile manufacture processes.

This may include production and sterilization by filtration of thebuffered solvent/solution used for the formulation, aseptic suspensionof the antibody in the sterile buffered solvent solution, and dispensingof the formulation into sterile receptacles by methods familiar to thoseof ordinary skill in the art.

Nebulizable formulation according to the present disclosure may beprovided, for example, as single dose units (e.g., sealed plasticcontainers or vials) packed in foil envelopes. Each vial contains a unitdose in a volume, e.g., 2 mL, of solvent/solution buffer.

The antibodies disclosed herein may be suitable for delivery vianebulisation.

It is also envisaged that the antibody of the present invention may beadministered by use of gene therapy. In order to achieve this, DNAsequences encoding the heavy and light chains of the antibody moleculeunder the control of appropriate DNA components are introduced into apatient such that the antibody chains are expressed from the DNAsequences and assembled in situ.

The present invention also provides an antibody molecule (orcompositions comprising same) for use in the control of autoimmunediseases, for example Acute Disseminated Encephalomyelitis (ADEM), Acutenecrotizing hemorrhagic leukoencephalitis, Addison's disease,Agammaglobulinemia, Alopecia areata, Amyloidosis, ANCA-associatedvasculitis, Ankylosing spondylitis, Anti-GBM/Anti-TBM nephritis,Antiphospholipid syndrome (APS), Autoimmune angioedema, Autoimmuneaplastic anemia, Autoimmune dysautonomia, Autoimmune hepatitis,Autoimmune hyperlipidemia, Autoimmune immunodeficiency, Autoimmune innerear disease (AIED), Autoimmune myocarditis, Autoimmune pancreatitis,Autoimmune retinopathy, Autoimmune thrombocytopenic purpura (ATP),Autoimmune thyroid disease, Autoimmune urticarial, Axonal & nalneuropathies, Balo disease, Behcet's disease, Bullous pemphigoid,Cardiomyopathy, Castleman disease, Celiac disease, Chagas disease,Chronic inflammatory demyelinating polyneuropathy (CIDP), Chronicrecurrent multifocal ostomyelitis (CRMO), Churg-Strauss syndrome,Cicatricial pemphigoid/benign mucosal pemphigoid, Crohn's disease,Cogans syndrome, Cold agglutinin disease, Congenital heart block,Coxsackie myocarditis, CREST disease, Essential mixed cryoglobulinemia,Demyelinating neuropathies, Dermatitis herpetiformis, Dermatomyositis,Devic's disease (neuromyelitis optica), Dilated cardiomyopathy, Discoidlupus, Dressler's syndrome, Endometriosis, Eosinophilic angiocentricfibrosis, Eosinophilic fasciitis, Erythema nodosum, Experimentalallergic encephalomyelitis, Evans syndrome, Fibrosing alveolitis, Giantcell arteritis (temporal arteritis), Glomerulonephritis, Goodpasture'ssyndrome, Granulomatosis with Polyangiitis (GPA) see Wegener's, Graves'disease, Guillain-Barre syndrome, Hashimoto's encephalitis, Hashimoto'sthyroiditis, Hemolytic anemia, Henoch-Schonlein purpura, Herpesgestationis, Hypogammaglobulinemia, Idiopathic hypocomplementemictubulointestitial nephritis, Idiopathic thrombocytopenic purpura (ITP),IgA nephropathy, IgG4-related disease, IgG4-related sclerosing disease,Immunoregulatory lipoproteins, Inflammatory aortic aneurysm,Inflammatory pseudotumour, Inclusion body myositis, Insulin-dependentdiabetes (typel), Interstitial cystitis, Juvenile arthritis, Juvenilediabetes, Kawasaki syndrome, Kuttner's tumour, Lambert-Eaton syndrome,Leukocytoclastic vasculitis, Lichen planus, Lichen sclerosus, Ligneousconjunctivitis, Linear IgA disease (LAD), Lupus (SLE), Lyme disease,chronic, Mediastinal fibrosis, Meniere's disease, Microscopicpolyangiitis, Mikulicz's syndrome, Mixed connective tissue disease(MCTD), Mooren's ulcer, Mucha-Habermann disease, Multifocalfibrosclerosis, Multiple sclerosis, Myasthenia gravis, Myositis,Narcolepsy, Neuromyelitis optica (Devic's), Neutropenia, Ocularcicatricial pemphigoid, Optic neuritis, Ormond's disease(retroperitoneal fibrosis), Palindromic rheumatism, PANDAS (PediatricAutoimmune Neuropsychiatric Disorders Associated with Streptococcus),Paraneoplastic cerebellar degeneration, Paraproteinemicpolyneuropathies, Paroxysmal nocturnal hemoglobinuria (PNH), ParryRomberg syndrome, Parsonnage-Turner syndrome, Pars planitis (peripheraluveitis), Pemphigus vulgaris, Periaortitis, Periarteritis, Peripheralneuropathy, Perivenous encephalomyelitis, Pernicious anemia, POEMSsyndrome, Polyarteritis nodosa, Type I, II, & III autoimmunepolyglandular syndromes, Polymyalgia rheumatic, Polymyositis,Postmyocardial infarction syndrome, Postpericardiotomy syndrome,Progesterone dermatitis, Primary biliary cirrhosis, Primary sclerosingcholangitis, Psoriasis, Psoriatic arthritis, Idiopathic pulmonaryfibrosis, Pyoderma gangrenosum, Pure red cell aplasia, Raynaudsphenomenon, Reflex sympathetic dystrophy, Reiter's syndrome, Relapsingpolychondritis, Restless legs syndrome, Retroperitoneal fibrosis(Ormond's disease), Rheumatic fever, Rheumatoid arthritis, Riedel'sthyroiditis, Sarcoidosis, Schmidt syndrome, Scleritis, Scleroderma,Sjogren's syndrome, Sperm & testicular autoimmunity, Stiff personsyndrome, Subacute bacterial endocarditis (SBE), Susac's syndrome,Sympathetic ophthalmia, Takayasu's arteritis, Temporal arteritis/Giantcell arteritis, Thrombotic, thrombocytopenic purpura (TTP), Tolosa-Huntsyndrome, Transverse myelitis, Ulcerative colitis, Undifferentiatedconnective tissue disease (UCTD), Uveitis, Vasculitis, Vesiculobullousdermatosis, Vitiligo, Waldenstrom Macroglobulinaemia, Warm idiopathichaemolytic anaemia and Wegener's granulomatosis (now termedGranulomatosis with Polyangiitis (GPA).

In one embodiment the antibodies or fragments according to thedisclosure are employed in the treatment or prophylaxis of epilepsy orseizures.

In one embodiment the antibodies or fragments according to thedisclosure are employed in the treatment or prophylaxis of multiplesclerosis.

In embodiment the antibodies and fragments of the disclosure areemployed in alloimmune disease/indications which includes:

-   -   Transplantation donor mismatch due to anti-HLA antibodies    -   Foetal and neonatal alloimmune thrombocytopenia, FNAIT (or        neonatal alloimmune thrombocytopenia, NAITP or NAIT or NAT, or        foeto-maternal alloimmune thrombocytopenia, FMAITP or FMAIT).

Additional indications include: rapid clearance of Fc-containingbiopharmaceutical drugs from human patients and combination of anti-FcRntherapy with other therapies—IVIg, Rituxan, plasmapheresis. For exampleanti-FcRn therapy may be employed following Rituxan therapy.

In embodiment the antibodies and fragments of the disclosure areemployed in a neurology disorder such as:

-   -   Chronic inflammatory demyelinating polyneuropathy (CIDP)    -   Guillain-Barre syndrome    -   Paraproteinemic polyneuropathies    -   Neuromyelitis optica (NMO, NMO spectrum disorders or NMO        spectrum diseases), and    -   Myasthenia gravis.

In embodiment the antibodies and fragments of the disclosure areemployed in a dermatology disorder such as:

-   -   Bullous pemphigoid    -   Pemphigus vulgaris    -   ANCA-associated vasculitis    -   Dilated cardiomyopathy

In embodiment the antibodies and fragments of the disclosure areemployed in an Immunology, haematology disorder such as:

-   -   Idiopathic thrombocytopenic purpura (ITP)    -   Thrombotic thrombocytopenic purpura (TTP)    -   Warm idiopathic haemolytic anaemia    -   Goodpasture's syndrome    -   Transplantation donor mismatch due to anti-HLA antibodies

In one embodiment the disorder is selected from Myasthenia Gravis,Neuro-myelitis Optica, CIDP, Guillaume-Barre Syndrome, Para-proteinemicPoly neuropathy, Refractory Epilepsy, ITP/TTP, Hemolytic Anemia,Goodpasture's Syndrome, ABO mismatch, Lupus nephritis, Renal Vasculitis,Sclero-derma, Fibrosing alveolitis, Dilated cardio-myopathy, Grave'sDisease, Type 1 diabetes, Auto-immune diabetes, Pemphigus, Sclero-derma,Lupus, ANCA vasculitis, Dermato-myositis, Sjogren's Disease andRheumatoid Arthritis.

In one embodiment the disorder is selected from autoimmune polyendocrinesyndrome types 1 (APECED or Whitaker's Syndrome) and 2 (Schmidt'sSyndrome); alopecia universalis; myasthenic crisis; thyroid crisis;thyroid associated eye disease; thyroid ophthalmopathy; autoimmunediabetes; autoantibody associated encephalitis and/or encephalopathy;pemphigus foliaceus; epidermolysis bullosa; dermatitis herpetiformis;Sydenham's chorea; acute motor axonal neuropathy (AMAN); Miller-Fishersyndrome; multifocal motor neuropathy (MMN); opsoclonus; inflammatorymyopathy; Isaac's syndrome (autoimmune neuromyotonia), Paraneoplasticsyndromes and Limbic encephalitis.

The antibodies and fragments according to the present disclosure may beemployed in treatment or prophylaxis.

The present invention also provides a method of reducing theconcentration of undesired antibodies in an individual comprising thesteps of administering to an individual a therapeutically effective doseof an anti-FcRn antibody or binding fragment thereof described herein.

In one embodiment the present disclosure comprises use of antibodies orfragments thereof as a reagent for diagnosis, for example conjugated toa reporter molecule. Thus there is provided antibody or fragmentaccording to the disclosure which is labelled. In one aspect there isprovided a column comprising an antibody or fragment according to thedisclosure.

Thus there is provided an anti-FcRn antibody or binding fragment for useas a reagent for such uses as:

-   -   1) purification of FcRn protein (or fragments thereof)—being        conjugated to a matrix and used as an affinity column, or (as a        modified form of anti-FcRn) as a precipitating agent (e.g. as a        form modified with a domain recognised by another molecule,        which may be modified by addition of an Fc (or produced as full        length IgG), which is optionally precipitated by an anti-Fc        reagent)    -   2) detection and/or quantification of FcRn on cells or in cells,        live or fixed (cells in vitro or in tissue or cell sections).        Uses for this may include quantification of FcRn as a biomarker,        to follow the effect of anti-FcRn treatment. For these purposes,        the candidate might be used in a modified form (e.g. by addition        of an Fc domain, as in full length IgG, or some other moiety, as        a genetic fusion protein or chemical conjugate, such as addition        of a fluorescent tag used for the purposes of detection).    -   3) purification or sorting of FcRn-bearing cells labeled by        binding to candidate modified by ways exemplified in (1) and        (2).

Also provided by the present invention is provided an assay suitable forassessing the ability of a test molecule such as an antibody molecule toblock FcRn activity and in particular the ability of the cells torecycle IgG. Such an assay may be useful for identifying inhibitors ofFcRn activity, such as antibody molecules or small molecules and as suchmay also be useful as a batch release assay in the production of such aninhibitor.

In one aspect there is provided an assay suitable for assessing theability of a test molecule such as an antibody molecule to block humanFcRn activity and in particular the ability of human FcRn to recycleIgG, wherein the method comprises the steps of:

-   -   a) coating onto a surface non-human mammalian cells        recombinantly expressing human FcRn alpha chain and human (32        microglobulin (β2M),    -   b) contacting the cells under mildly acidic conditions such as        about pH5.9 with a test molecule and an IgG to be recycled by        the cell for a period of time sufficient to allow binding of        both the test molecule and the IgG to FcRn, optionally adding        the test molecule before the IgG to be recycled and incubating        for a period of time sufficient to allow binding of the test        molecule to FcRn.    -   c) washing with a slightly acidic buffer, and    -   d) detecting the amount of IgG internalised and/or recycled by        the cells.

In one aspect there is provided an assay suitable for assessing theability of a test molecule such as an antibody molecule to block humanFcRn activity and in particular the ability of human FcRn to recycleIgG, wherein the method comprises the steps of:

-   -   a) coating onto a surface non-human mammalian cells        recombinantly expressing human FcRn alpha chain and human (32        microglobulin (β2M),    -   b) contacting the cells under mildly acidic conditions such as        about pH5.9 with a test antibody molecule and an IgG to be        recycled by the cell for a period of time sufficient to allow        binding of both the test antibody molecule and the IgG to FcRn,        optionally adding the test antibody molecule before the IgG to        be recycled and incubating for a period of time sufficient to        allow binding of the test antibody molecule to FcRn.    -   c) washing with a slightly acidic buffer to remove unbound IgG        and test antibody molecule, and    -   d) detecting the amount of IgG recycled by the cells.

In one aspect there is provided an assay suitable for assessing theability of a test molecule such as an antibody molecule to block humanFcRn activity and in particular the ability of human FcRn to recycleIgG, wherein the method comprises the steps of:

-   -   a) coating onto a surface non-human mammalian cells        recombinantly expressing human FcRn alpha chain and human (32        microglobulin (β2M),    -   b) contacting the cells under mildly acidic conditions such as        about pH5.9 with a test antibody molecule and an IgG to be        recycled by the cell for a period of time sufficient to allow        binding of both the test antibody molecule and IgG to FcRn,        optionally adding the test antibody molecule before the IgG to        be recycled and incubating for a period of time sufficient to        allow binding of the test antibody molecule to FcRn.    -   c) washing with a slightly acidic buffer to remove unbound IgG        and test antibody molecule,    -   d) incubating the cells in a neutral buffer such as about pH 7.2    -   e) detecting the amount of IgG recycled by the cells by        determining the amount of IgG released into the supernatant.

Suitable cells include Madin-Darby Canine Kidney (MDCK) II cells.Transfection of MDCKII cells with human FcRn alpha chain and human (32microglobulin (β2M) has previously been described by Claypool et al.,2002, Journal of Biological Chemistry, 277, 31, 28038-28050. This paperalso describes recycling of IgG by these transfected cells.

Media for supporting the cells during testing includes complete mediacomprising MEM (Gibco #21090-022), 1× non-essential amino acids (Gibco11140-035), 1× sodium pyruvate (Gibco #11360-039), and L-glutamine(Gibco #25030-024).

Acidic wash can be prepared by taking HBSS+(PAA #H15-008) and adding 1MMES until a pH 5.9+/−0.5 is reached. BSA about 1% may also be added(Sigma #A9647).

A neutral wash can be prepared by taking HBSS+(PAA #H15-008) and adding10M Hepes pH 7.2+/−0.5 is reached. BSA about 1% may also be added (Sigma#A9647).

Washing the cells with acidic buffer removes the unbound test antibodyand unbound IgG and allows further analysis to be performed. Acidicconditions used in step (b) encourage the binding of the IgG to FcRn andinternalisation and recycling of the same.

The amount of test antibody or fragment and IgG on only the surface ofthe cells may be determined by washing the cells with neutral wash andanalysing the supernatant/washings to detect the quantity of testantibody or IgG. Importantly a lysis buffer is not employed. Todetermine the amount of IgG internalised by the cells the antibody mayfirst be removed from the surface of the cell with a neutral wash andthe cells lysed by a lysis buffer and then the internal contentsanalysed. To determine the amount of IgG recycled by the cells the cellsare incubated under neutral conditions for a suitable period of time andthe surrounding buffer analysed for IgG content. If the surface andinternal antibody content of the cell is required then the cell can bewashed with acid wash to maintain the antibody presence on the cellsurface, followed by cell lysis and analysis of the combined material.

Where it is desired to measure both internalisation and recycling of theIgG samples are run in duplicate and testing for internalisation andrecycling conducted separately.

A suitable lysis buffer includes 150 mM NaCl, 20 mM Tris, pH 7.5, 1 mMEDTA, 1 mM EGTA, 1% Triton-X 100, for each 10 ml add proteaseinhibitors/phosphate inhibitors as described in manufacturer'sguidelines.

Typically the IgG to be recycled is labelled, in one example abiotinylated human IgG may be used. The IgG can then be detectedemploying, for example a streptavidin sulfo-tag detection antibody (suchas MSD #r32ad-5) 25 mL at 0.2 ug/mL of MSD blocking buffer. Blockingbuffer may comprise 500 mM Tris, pH7.5. 1.5M NaCl and 0.2% Tween-20 and1.5% BSA.

Alternatively the IgG may be pre-labelled with a fluorophore or similarlabel.

In one embodiment a suitable surface is a plastic plate or well such asa 96 well plate or similar, a glass slide or a membrane. In one examplecells are coated onto the surface at a density that results in theformation of a monolayer.

In one embodiment the assay described herein is not a measurement oftranscytosis of an antibody top to bottom across a membrane with a pHgradient there-across, for example acid conditions one side of themembrane and neutral conditions on the underside of the membrane.

In one example the test antibody or fragment and IgG may be incubatedwith the cells in step (b) for about 1 hour for example at ambienttemperature under acidic conditions to allow binding.

In one example the test antibody or fragment may be incubated with thecells in step (b) for about 1 hour for example at ambient temperatureunder acidic conditions to allow binding before addition of the IgG tobe recycled. Subsequently the IgG to be recycled by the cell may beincubated with the cells in step (b) for about 1 hour for example atambient temperature under acidic conditions to allow binding.

Neutral conditions facilitate release of the IgG into the supernatant.

Comprising in the context of the present specification is intended tomeaning including.

Where technically appropriate embodiments of the invention may becombined.

Embodiments are described herein as comprising certainfeatures/elements. The disclosure also extends to separate embodimentsconsisting or consisting essentially of said features/elements.

Technical references such as patents and applications are incorporatedherein by reference.

The present invention is further described by way of illustration onlyin the following examples, which refer to the accompanying Figures, inwhich:

FIG. 1 shows certain amino acid and polynucleotide sequences.

FIG. 2 shows alignments of certain sequences.

FIG. 3 shows a comparison of binding on human MDCK II for a Fab′fragment according to the present disclosure and a PEGylated versionthereof

FIG. 4 shows a Fab′ fragment according to the present disclosure and aPEGylated version thereof inhibiting IgG recycling on MDCK II cells

FIG. 5 shows a PEGylated Fab′ fragment according to the presentdisclosure inhibits apical to basolateral IgG transcytosis in MDCK IIcells

FIG. 6 shows a comparison of binding of cyno monkey MDCK II for a Fab′fragment according to the present disclosure and a PEGylated versionthereof

FIG. 7 shows a PEGylated Fab′ fragment according to the presentinhibiting IgG recycling on MDCK II cells for human and cyno monkeyversions thereof

FIG. 8 shows the effect of a single dose of a PEGylated Fab′ moleculeaccording to the disclosure on plasma IgG levels in cynomolgus monkeys

FIG. 9 shows the effect of four weekly doses of a PEGylated Fab′molecule according to the disclosure on plasma IgG levels

FIG. 10 shows a diagrammatic representation of antibody recyclingfunction of FcRn inhibited by a blocking protein

FIG. 11 shows flow cytometry based human IgG blocking assay usingpurified gamma 1 IgG antibodies

FIG. 12 shows Fab′PEG single/intermittent IV doses in normal cyno 20mg/Kg days 1 and 67 IgG pharmacodynamics

FIG. 13 shows Fab′PEG: repeat IV doses in normal cyno-4×20 or 100 mg/Kgper week IgG pharmacodynamics

FIG. 14 shows Fab′PEG single/intermittent IV doses in normal cyno −20mg/Kg and 100 mg/Kg days 1 and 67 IgG Pharmacodynamics

FIG. 15 shows plasma IgG levels in 4 cynomolgus monkeys after 2 IV dosesof 20 mg/Kg 1519.g57 Fab′PEG

FIG. 16 shows plasma IgG levels in 4 cynomolgus monkeys receiving 10 IVdoses of 20 mg/Kg 1519.g57 Fab′PEG, one every 3 days

FIG. 17 shows the effect of two 30 mg/Kg IV doses of 1519.g57 IgG4P onthe endogenous plasma IgG in cynomolgus monkeys

FIG. 18 shows the effect of 30 mg/Kg if followed by 41 daily doses of 5mg/Kg 1519.g57 IgG4P on plasma IgG in cynomolgus monkeys

FIG. 19 shows the result of daily dosing with vehicle on the plasma IgGin cynomolgus monkeys

FIG. 20 shows the increased clearance of IV hIgG in plasma of hFcRntransgenic mice treated with CA170_01519.g57 Fab′PEG or PBS IV

FIG. 21 shows the increased clearance of IV hIgG in plasma of hFcRntransgenic mice treated with CA170_01519.g57 IgG1 or IgG4 or PBS IV

FIG. 22 shows the increased clearance of IV hIgG in plasma of hFcRntransgenic mice treated with CA170_01519.g57 Fab′-human serum albumin orPBS IV

FIG. 23 shows the increased clearance of IV hIgG in plasma of hFcRntransgenic mice treated with CA170_01519.g57 FabFv or PBS IV

FIG. 24 shows the increased clearance of IV hIgG in plasma of hFcRntransgenic mice treated with CA170_01519.g57 Fab or Fab′PEG or PBS IV

FIG. 25 shows a bispecific antibody fusion protein of the presentinvention, referred to as a Fab-dsFv.

EXAMPLES

The following immunizations were performed in order to generate materialfor B cell culture and antibody screening:

Sprague Dawley rats were immunized with three shots of NIH3T3 mousefibroblasts co-expressing mutant human FcRn (L320A; L321A) (Ober et al.,2001 Int. Immunol. 13, 1551-1559) and mouse β2M with a fourth finalboost of human FcRn extracellular domain. Sera were monitored for bothbinding to mutant FcRn on HEK-293 cells and for its ability to preventbinding of Alexafluor 488-labelled human IgG. Both methods wereperformed by flow cytometry. For binding, phycoerythrin (PE)-labelledanti mouse or rat Fc specific secondary reagents were used to revealbinding of IgG in sera.

B cell cultures were prepared using a method similar to that describedby Zubler et al. (1985). Briefly, B cells at a density of approximately5000 cells per well were cultured in bar-coded 96-well tissue cultureplates with 200 μl/well RPMI 1640 medium (Gibco BRL) supplemented with10% FCS (PAA laboratories ltd), 2% HEPES (Sigma Aldrich), 1% L-Glutamine(Gibco BRL), 1% penicillin/streptomycin solution (Gibco BRL), 0.1%β-mercaptoethanol (Gibco BRL), 2-5% activated rabbit splenocyte culturesupernatant and gamma-irradiated EL-4-B5 murine thymoma cells(5×10⁴/well) for seven days at 37° C. in an atmosphere of 5% CO₂. Thepresence of FcRn-specific antibodies in B cell culture supernatants wasdetermined using a homogeneous fluorescence-based binding assay usingHEK-293 cells transiently transfected with mutant FcRn(surface-stabilised) as a source of target antigen. 10 ul of supernatantwas transferred from barcoded 96-well tissue culture plates intobarcoded 384-well black-walled assay plates containing 5000 transfectedHEK-293 cells per well using a Matrix Platemate liquid handler. Bindingwas revealed with a goat anti-rat or mouse IgG Fcγ-specific Cy-5conjugate (Jackson). Plates were read on an Applied Biosystems 8200cellular detection system. From 3800×96-well culture plates,representing 38 different immunized animals, 9800 anti-human FcRnbinders were identified. It was estimated that this represented thescreening of approximately 2.5 billion B cells.

Following primary screening, positive supernatants were consolidated on96-well bar-coded master plates using an Aviso Onyx hit-picking robotand B cells in cell culture plates frozen at −80 C. Master plates werethen screened in a Biacore assay in order to identify wells containingantibodies of high affinity and those which inhibited the binding ofhuman IgG to FcRn (see below).

Biomolecular interaction analysis using surface plasmon resonancetechnology (SPR) was performed on a BIAcore T200 system (GE Healthcare).Goat anti-rat IgG, Fc gamma (Chemicon International Inc.) in 10 mM NaAc,pH 5 buffer was immobilized on a CMS Sensor Chip via amine couplingchemistry to a capture level of approx. 19500 response units (RU) usingHBS-EP⁺ as the running buffer. 50 mM Phosphate, pH6+150 mM NaCl was usedas the running buffer for the affinity and blocking assay. B cellculture supernatants were diluted 1 in 5 in 200 mM Phosphate, pH6+150 mMNaCl. A 600 s injection of diluted B cell supernatant at 5 μl/min wasused for capture by the immobilized anti-rat IgG, Fc. Human FcRn at 100nM was injected over the captured B cell culture supernatant for 180 sat 30 μl/min followed by 360 s dissociation. Human IgG (JacksonImmunoResearch) was injected over for 60 s with 180 s dissociation at 30μl/min.

The data was analysed using T200 evaluation software (version 1.0) todetermine affinity constants (K_(D)) of antibodies and determine thosewhich blocked IgG binding.

As an alternative assay, master plate supernatants were also screened ina cell-based human IgG blocking assay. 25 ul of B cell culturesupernatant from master plates were added to 96 well U-bottomedpolypropylene plate. Mutant hFcRn-transfected HEK-293 cells (50,000cells per well in 25 ul PBS pH6/1% FCS) were then added to each well andincubated for 1 hour at 4° C. Cells were washed twice with 150 ul of PBSmedia. Cells were then resuspended in 50 ul/well PBS/FCS mediacontaining human IgG labelled with Alexafluor 488 or 649 at 7.5 ug/mland incubated 1 hour at 4° C. Cells were then washed twice with 150 ulof media and then resuspended in 35 ul/well of PBS/FCS media containing1% formaldehyde as fixative. Plates were then read on a FACS Canto 2flow cytometer. Example data is given in FIG. 11 .

To allow recovery of antibody variable region genes from a selection ofwells of interest, a deconvolution step had to be performed to enableidentification of the antigen-specific B cells in a given well thatcontained a heterogeneous population of B cells. This was achieved usingthe Fluorescent foci method. Briefly, Immunoglobulin-secreting B cellsfrom a positive well were mixed with streptavidin beads (New EnglandBiolabs) coated with biotinylated human FcRn and a 1:1200 final dilutionof a goat anti-rat or mouse Fcγ fragment-specific FITC conjugate(Jackson). After static incubation at 37° C. for 1 hour,antigen-specific B cells could be identified due to the presence of afluorescent halo surrounding that B cell. These individual B cells,identified using an Olympus microscope, were then picked with anEppendorf micromanipulator and deposited into a PCR tube. Fluorescentfoci were generated from 268 selected wells.

Antibody variable region genes were recovered from single cells byreverse transcription polymerase chain reaction (RT)-PCR using heavy andlight chain variable region-specific primers. Two rounds of PCR wereperformed on an Aviso Onyx liquid handling robot, with the nested 2° PCRincorporating restriction sites at the 3′ and 5′ ends allowing cloningof the variable regions into a mouse γ1 IgG (VH) or mouse kappa (VL)mammalian expression vector. Paired heavy and light chain constructswere co-transfected into HEK-293 cells using Fectin 293 (Invitrogen) andcultured in 48-well plates in a volume of 1 ml. After 5-7 daysexpression, supernatants were harvested and antibody subjected tofurther screening.

PCR successfully recovered heavy and light chain cognate pairs fromsingle B cells from 156 of the selected wells. DNA sequence analysis ofthe cloned variable region genes identified a number of unique familiesof recombinant antibody. Following expression, transient supernatantswere interrogated in both human IgG FACS blocking (described above) andIgG recycling assays. In some cases, purified mouse γ1 IgG was producedand tested (data labeled accordingly).

The recycling assay used MDCK II cells (clone 34 as described inExamples 4 and 5 below) over-expressing human FcRn and beta 2microglobulin plated out at 25,000 cells per well of a 96 well plate.These were incubated overnight at 37° C., 5% CO₂. The cells were washedwith HBSS+Ca/Mg pH 7.2+1% BSA and then incubated with 50 μl of varyingconcentrations of HEK-293 transient supernatant or purified antibody for1 hour at 37° C., 5% CO₂. The supernatant was removed and 500 ng/ml ofbiotinylated human IgG (Jackson) in 50 μl of HBSS+Ca/Mg pH 5.9+1% BSAwas added to the cells and incubated for 1 hour at 37° C., 5% CO₂. Thecells were then washed three times in HBSS+Ca/Mg pH 5.9 and 100 μl ofHBSS+Ca/Mg pH 7.2 added to the cells and incubated at 37° C., 5% CO₂ for2 hours. The supernatant was removed from the cells and analysed fortotal IgG using an MSD assay with an anti-human IgG capture antibody(Jackson) and a streptavidin-sulpho tag reveal antibody (MSD). Theinhibition curve was analysed by non-linear regression to determine IC50values. Based on performance in these assays a family of antibodies wasselected comprising the six CDRs given in SEQ ID NOs 1 to 6. AntibodyCA170_01519 had the best activity and was selected for humanisation.

Example 1 Humanisation Method

Antibody CA170_01519 was humanised by grafting the CDRs from the ratantibody V-regions onto human germline antibody V-region frameworks. Inorder to recover the activity of the antibody, a number of frameworkresidues from the rat V-regions were also retained in the humanisedsequence. These residues were selected using the protocol outlined byAdair et al. (1991) (Humanised antibodies WO91/09967). Alignments of therat antibody (donor) V-region sequences with the human germline(acceptor) V-region sequences are shown in FIGS. 2A and 2B, togetherwith the designed humanised sequences. The CDRs grafted from the donorto the acceptor sequence are as defined by Kabat (Kabat et al., 1987),with the exception of CDR-H1 where the combined Chothia/Kabat definitionis used (see Adair et al., 1991 Humanised antibodies. WO91/09967). HumanV-region VK1 2-1-(1) A30 plus JK2 J-region (V BASE,vbase.mrc-cpe.cam.ac.uk/) was chosen as the acceptor for the light chainCDRs. Human V-region VH3 1-3 3-07 plus JH4 J-region (V BASE,vbase.mrc-cpe.cam.ac.uk/) was chosen as the acceptor for the heavy chainCDRs.

Genes encoding a number of variant heavy and light chain V-regionsequences were designed and these were constructed by an automatedsynthesis approach by Entelechon GmbH. Further variants of both heavyand light chain V-regions were created by modifying the VH and VK genesby oligonucleotide-directed mutagenesis. These genes were cloned into anumber of vectors to enable expression of humanised 1519 Fab′ inmammalian and E. coli cells. The variant chains, and combinationsthereof, were assessed for their expression in E. coli, their potencyrelative to the parent antibody, their biophysical properties andsuitability for downstream processing, leading to the selection of thegL20 light chain graft and gH2O heavy chain graft. The final selectedgL20 and gH2O graft sequences are shown in FIGS. 2A and 2B,respectively. This V-region pairing was named 1519.g57.

The light chain framework residues in graft gL20 are all from the humangermline gene, with the exception of residues 36, 37 and 58 (Kabatnumbering), where the donor residues Leucine (L36), Phenylalanine (F37)and Isoleucine (158) were retained, respectively. Retention of thesethree residues was essential for full potency of the humanised Fab′. Theheavy chain framework residues in graft gH2O are all from the humangermline gene, with the exception of residues 3, 24, 76, 93 and 94(Kabat numbering), where the donor residues Proline (P3), Valine (V24),Serine (S76), Threonine (T93) and Threonine (T94) were retained,respectively. Retention of these five residues was important for fullpotency of the humanised Fab′.

For expression in E. coli, the humanised heavy and light chain V-regiongenes were cloned into the UCB expression vector pTTOD, which containsDNA encoding the human C-kappa constant region (Km3 allotype) and thehuman gamma-1 CH1-hinge region (G1m17 allotype). The E. coli FkpA genewas also introduced into the expression plasmid, as co-expression ofthis chaperone protein was found to improve the yield of the humanisedFab′ in E. coli strain MXE016 (disclosed in WO2011/086136) duringbatch-fed fermentation, using IPTG to induce Fab′ expression. The 1519Fab′ light and heavy chains and FkpA polypeptide were all expressed froma single multi-cistron under the control of the IPTG-inducible tacpromoter.

For expression in mammalian cells, the humanised light chain V-regiongenes were cloned into the UCB-Celltech human light chain expressionvector pMhCK, which contains DNA encoding the human Kappa chain constantregion (Km3 allotype). The humanised heavy chain V-region genes werecloned into the UCB-Celltech human gamma-4 heavy chain expression vectorpMhg4P FL, which contains DNA encoding the human gamma-4 heavy chainconstant region with the hinge stabilising mutation S241P (Angal et al.,Mol Immunol. 1993, 30(1):105-8). Co-transfection of light and heavychain vectors into HEK293 suspension cells was achieved using 293 Fectin(12347-019 Invitrogen), and gave expression of the humanised,recombinant 1519 antibodies.

Example 1A Preparation of 1519.g57 Fab′-PEG Conjugate

Fab′ expressed in the periplasm of E. coli was extracted from cells byheat extraction. Fab′ purified by Protein G affinity purification withan acid elution. Fab′ reduced and PEGylated with 40 kDa PEG (SUNBRIGHTGL2-400MA3). PEG is covalently linked via a maleimide group to one ormore thiol groups in the antibody fragment. PEGylation efficiency wasconfirmed by SE-HPLC. Fab′PEG was separated from un-PEGylated Fab′ anddiFab′ by cation exchange chromatography. Fractions analyzed by SE-HPLCand SDS-PAGE. Pooling carried out to minimize levels of impurities.Final sample concentrated and diafiltered into desired buffer.

Example 1B Preparation of 1519.g57 Fab′ (Anti Human FcRn) Conjugatedwith Human Serum Albumin

Anti human FcRn Fab′ 1519.g57 was chemically conjugated with human serumalbumin (recombinant derived) which was then used for animal studies.

-   -   Human serum albumin: Recombumin from Novozyme (Cat No: 200-010)        presented as 20% w/v solution produced recombinantly in        Saccharomyces cerevisiae.    -   1519.g57Fab′: 30 mg/ml presented in 0.1M Sodium Phosphate, 2 mM        EDTA, pH6.0 (reduction buffer)    -   1,6-Bismaleimidohexane (BMH) from Thermofisher (Cat No. 22330)

Reduction of Albumin:

Albumin was reduced using freshly prepared cysteamine hydrochloride(Sigma cat no: 30078) which was prepared in reduction buffer. To thealbumin solution cysteamine hydrochloride was added at 10 fold molarexcess and then incubated at 37° C. water bath for 30 minutes. Followingreduction the solution was desalted using PD10 columns (GE HealthcareCat. No: 17-0851-01) to remove any excess reducing agent.

Addition of BMH Linker:

A stock solution of 1,6-bismaleimidohexane was prepared in glass vialusing dimethylformamide. The solution was vortexed to ensure completedissolution of BMH. BMH solution was added to the desalted reducedalbumin solution at 10 fold molar excess with respect to albuminconcentration. The solution was then incubated at 37° C. for 30 minutesfollowed by overnight incubation at room temperature on a roller toensure proper mixing. A white precipitate was seen which was spun downusing bench top centrifuge. After the completion of the reaction thesolution was desalted using PD10 columns.

Reduction of 1519.g57 Fab′

1519.g57 Fab′ was reduced using freshly prepared cysteaminehydrochloride (Sigma cat no: 30078) which was prepared in reductionbuffer. To the 1519.g57 Fab′ solution cysteamine hydrochloride was addedat 10 fold molar excess and then incubated at 37° C. water bath for 30minutes. Following reduction the solution was desalted using PD10columns (from GE Healthcare Cat. No: 17-0851-01) to remove any excessreducing agent.

Mixing of Reduced Fab and Albumin-BMH

Equal amounts (in molar terms) of the reduced Fab′ and albumin-linkerwas added and incubated at room temperature overnight on a roller mixer.

Affinity Purification:

The above mix was then affinity purified using Blue Sepharose whichbound to albumin-Fab conjugate and free albumin. Purification wascarried out according to manufacturer's instruction which is brieflydescribed here:

Blue sepharose was reconstituted in DPBS pH7.4 and washed thrice withPBS. Following washing the mixture of Fab and linker linked albumin wasadded and incubated at room temperature for 1 hour on a roller mixer.After incubation the matrix was washed again with PBS to remove anyunbound materials and then eluted with PBS7.4 containing 2M KCl.

Size Exclusion Purification:

The affinity purified material contained albumin conjugated to Fab alongwith some unreacted HSA. This required further clean-up and this wasachieved using size exclusion chromatography (S200 16 X60 from GEHealthcare). The final pooled fractions were presented in DPBS pH7.4.

The final 1519.g57Fab-HSA conjugate was concentrated up to 20 mg/ml inDPBS pH7.4 and analyzed on analytical size exclusion chromatography(Agilent Zorbax GF250 and GF450 in tandem) and was found to bepredominantly monomeric conjugate. Endotoxin assay was also carried outand the sample was found to be below the specified lower limit ofendotoxin content.

Example 2 Screening of Fab′ & Fab′PEG Candidate Molecules in the IgGRecycling Assay

To determine the ability of the candidate Fab′PEG molecules to blockFcRn activity in a functional cell assay, the molecules were screened inthe IgG recycling assay (described in more detail in Example 5).Briefly, MDCK II clone 34 cells were pre-incubated with candidate Fab′or Fab′PEG before addition of biotinylated human IgG in an acidicbuffer. The cells were washed to remove all excess IgG and thenincubated in a neutral pH buffer to facilitate release of IgG into thesupernatant. The amount of IgG released into the supernatant wasmeasured by MSD assay and EC₅₀ values calculated. The EC₅₀ values ofhumanised Fab′ and Fab′PEG candidate molecules that inhibit IgGrecycling are shown in the table below. Upon PEGylation there is a lossof potency for all candidate antibodies, however the extent of thisvaries depending on candidate.

TABLE 1 Fab'PEG Fold Change Fab' EC₅₀ EC₅₀ in EC₅₀ Antibody (nM) (n)(nM) (n) after pegylation CA170 0519.g63 1.91 3  5.25 3 2.7 CA1700519.g57 2.06 7  6.64 6 3.2 CA170 0519.g2 4.22 2 11.01 4 2.6

Mean EC₅₀ Values for Fab′ and Fab′PEG Molecules in the IgG RecyclingAssay.

MDCK II clone 34 cells stably transfected with human FcRn and beta 2microglobulin were at 25,000 cells per well in a 96 well plate andincubated overnight at 37° C., 5% CO₂. The cells were incubated withcandidate Fab′ or Fab′PEG in HBSS⁺ (Ca/Mg) pH 5.9+1% BSA for 1 hour at37° C., 5% CO₂ before addition of 500 ng/ml of biotinylated human IgG(Jackson) and incubation for a further 1 hour. The cells were washedwith HBSS⁺ pH 5.9 and then incubated at 37° C., 5% CO₂ for 2 hours inHBSS⁺ pH 7.2. The supernatant was removed from the cells and analysedfor total IgG using an MSD assay (using an anti-human IgG captureantibody (Jackson) and a streptavidin-sulpho tag reveal antibody (MSD)).The inhibition curve was analysed by non-linear regression (GraphpadPrism®) to determine the EC₅₀. Table 1 represents combined data from 2to 7 experiments.

Example 3 Affinity for hFcRn Binding

Biomolecular interaction analysis using surface plasmon resonancetechnology (SPR) was performed on a Biacore T200 system (GE Healthcare)and binding to human FcRn extracellular domain determined. Human FcRnextracellular domain was provided as a non-covalent complex between thehuman FcRn alpha chain extracellular domain (SEQ ID NO:94) and (32microglobulin (β2M) (SEQ ID NO:95). Affinipure F(ab′)₂ fragment goatanti-human IgG, F(ab′)₂ fragment specific (for Fab′-PEG capture) or Fcfragment specific (for IgG1 or IgG4 capture) (Jackson ImmunoResearchLab, Inc.) in 10 mM NaAc, pH 5 buffer was immobilized on a CMS SensorChip via amine coupling chemistry to a capture level between 4000-5000response units (RU) using HBS-EP⁺ (GE Healthcare) as the running buffer.

50 mM Phosphate, pH6+150 mM NaCl+0.05% P20 or HBS-P, pH7.4 (GEHealthcare) was used as the running buffer for the affinity assay. Therelevant antibody, either anti-hFcRn Fab′-PEG, IgG1 or IgG4P was dilutedto 5 μg/ml (Fab′-PEG), 0.3 μg/ml (IgG1) or 4 μg/ml (IgG4) in runningbuffer. A 60 s injection of Fab′-PEG or IgG1 or IgG4 at 10 μl/min wasused for capture by the immobilized anti-human IgG, F(ab′)₂. Human FcRnextracellular domain was titrated from 20 nM to 1.25 nM over thecaptured anti-FcRn antibody (Fab′-PEG, IgG1 or IgG4) for 300 s at 30μl/min followed by 1200 s dissociation. The surface was regenerated by2×60 s 50 mM HCl at 10 μl/min.

The data was analysed using T200 evaluation software (version 1.0).

TABLE 2 Affinity data for anti-hFcRn 1519.g57 Fab'-PEG at pH61519.g57Fab'-PEG ka (M⁻¹s⁻¹) kd (s⁻¹) KD (M) 1 4.37E+05 1.59E−053.63E−11 2 4.20E+05 2.01E−05 4.78E−11 3 4.35E+05 1.43E−05 3.29E−11 44.37E+05 2.75E−05 6.30E−11 5 4.33E+05 1.28E−05 2.97E−11 4.32E+051.81E−05 4.19E−11

TABLE 3 Affinity data for anti-hFcRn 1519.g57 Fab’-PEG at pH7.41519.g57Fab'-PEG ka (M⁻¹s⁻¹) kd (s⁻¹) Kd(M) 1 3.40E+05 1.87E−05 5.49E−112 3.31E+05 1.85E−05 5.58E−11 3 3.25E+05 1.99E−05 6.13E−11 4 3.23E+051.52E−05 4.70E−11 5 3.20E+05 1.99E−05 6.21E−11 3.28E+05 1.84E−055.62E−11

In these experiments the Fab′PEG had an average affinity of around 42 pMat pH6 and around 56 pM at pH7.4.

TABLE 3A Affinity data for anti-hFcRn 1519.g57 as IgGl and IgG4P atpH7.4 (average of three experiments) pH7.4 1519.g57 ka (M⁻¹s⁻¹) kd (s⁻¹)KD (M) KD (pM) IgG1 3.80E+05 1.25E−05 3.29E−11 33 IgG4P 3.68E+051.26E−05 3.43E−11 34

TABLE 3B Affinity data for anti-hFcRn 1519.g57 as IgGl and IgG4P at pH6(average of three experiments) pH6 1519.g57 ka (M⁻¹s⁻¹) kd (s⁻¹) KD (M)KD (pM) IgG1 4.56E+05 1.01E-05 2.21E−11 22 lgG4P 4.43E+05 1.00E-052.26E−11 23

Tables 3A and 3B show the affinity of the full length antibodies isconsistent with that observed for the Fab′-PEG at both pH6 and pH7.4.

Example 4 Cell-Based Potency

Cell-based assays were performed using Madin-Darby Canine Kidney (MDCK)II cells which had been stably transfected with a human FcRn and humanB2M double gene vector with a Geneticin selection marker. A stable cellclone was selected that was able to recycle and transcytose human IgGand this was used for all subsequent studies. It will be referred to asMDCK II clone 34.

Cell Based Affinity of CA170_01519.g57 Fab′PEG for Human FcRn

Quantitative flow cytometry experiments were performed using MDCK IIclone 34 cells and AlexaFluor 488-labelled CA170_01519.g57 Fab′ orCA170_01519.g57 Fab′PEG. Specific binding of antibody to FcRn across arange of antibody concentrations was used to determine K_(D). Theanalyses were performed in both neutral and acidic buffers to determinewhether environmental pH comparable to that found in blood plasma(pH7.4) or endosomes (pH6) had any effect on the antibody binding.

FIG. 3 shows representative binding curves for CA170_01519.g57 Fab′(FIG.3A) and Fab′PEG (FIG. 3B). The mean K_(D) values (n=2 or 3) were 1.66 nMand 6.5 nM in neutral buffer, and 1.59 nM and 5.42 nM in acidic buffer,respectively (see Table 4).

TABLE 4 Mean K_(D) values (nM) for CA170_01519.g57 Fab' and Fab'PEG onMDCKII clone 34 cells. Antibody format Human FcRnpH 7.4 Human FcRnpH 6.01519.g57 Fab′ 1.66 1.59 1519.g57 Fab′PEG 6.5 5.42

FIG. 3 shows CA170_01519.g57 Fab′ (A) and CA170_01519.g57 Fab′PEG (B)binding on MDCK II clone 34 cells in acidic and neutral pH.

MDCK II clone 34 cells were incubated in Facs buffer (PBS with 0.2% w/vBSA, 0.09% w/v NaN3) for 30 mins prior to the addition of Alexa-fluor488-labelled CA170_01519.g57 Fab′ or Fab′PEG for 1 hour in Facs bufferat either pH 7.4 or pH 6. The final antibody concentrations ranged from931 nM to 0.002 nM. The cells were washed in ice cold Facs buffer thenanalysed by flow cytometry using a Guava flow cytometer (Millipore, UK).

Titration data sets were also produced for isotype control antibodiesfor each antibody format to determine non-specific binding. The numberof moles of bound antibody was calculated using interpolated values froma standard curve generated from beads comprised of differing amounts offluorescent dye. Geometric mean fluorescence values were determined inthe flow cytometric analyses of cells and beads. Non-specific bindingwas subtracted from the anti-FcRn antibody values and the specificbinding curve generated was analysed by non-linear regression using aone-site binding equation (Graphpad Prism®) to determine the K_(D). Datais representative of 2 or 3 experiments.

CA170_01519.g57 Fab′PEG can bind human FcRn expressed on cells at bothacidic and neutral pH and the determined K_(D) values are approximately3.5 to 4 fold below the equivalent Fab′ molecule.

Example 5 Functional Cell Based Assays

CA170_01519.g57 Fab′PEG inhibits the recycling of human IgG FcRnexpression is primarily intracellular (Borvak J et al. 1998, Int.Immunol., 10 (9) 1289-98 and Cauza K et al. 2005, J. Invest. Dermatol.,124 (1), 132-139), and associated with endosomal and lysosomalmembranes. The Fc portion of IgG binds to FcRn at acidic pH (<6.5), butnot at a neutral physiological pH (7.4) (Rhagavan M et al. 1995) andthis pH-dependency facilitates the recycling of IgG.

Once it is taken up by pinocytosis and enters the acidic endosome, IgGbound to FcRn will be recycled along with the FcRn to the cell surface,whereas at the physiologically neutral pH the IgG will be released.(Ober R J et al. 2004, The Journal of Immunology, 172, 2021-2029). AnyIgG not bound to FcRn will enter the lysosomal degradative pathway.

An in vitro assay was established to examine the ability ofCA170_01519.g57 Fab′PEG or Fab′ to inhibit the IgG recyclingcapabilities of FcRn. Briefly, MDCK II clone 34 cells were incubated inthe presence or absence of CA170_01519.g57 Fab′ or CA170_01519.g57Fab′PEG before addition of biotinylated human IgG in an acidic buffer(pH 5.9) to allow binding to FcRn. All excess antibody was removed andthe cells incubated in a neutral pH buffer (pH 7.2) which allows releaseof surface-exposed, bound IgG into the supernatant. The inhibition ofFcRn was followed using an MSD assay to detect the amount of IgGrecycled and thus released into the supernatant.

FIG. 4 shows CA170_01519.g57 inhibits IgG recycling in MDCK II clone 34cells. MDCK II clone 34 cells were plated at 25,000 cells per well in a96 well plate and incubated overnight at 37° C., 5% CO₂. The cells wereincubated with CA170_01519.g57 Fab′ or Fab′PEG in HBSS⁺ (Ca/Mg) pH5.9+1% BSA for 1 hour at 37° C., 5% CO₂ before addition of 500 ng/ml ofbiotinylated human IgG (Jackson) and incubation for a further 1 hour.The cells were washed with HBSS⁺ pH 5.9 then incubated at 37° C., 5% CO₂for 2 hours in HBSS⁺ pH 7.2. The supernatant was removed from the cellsand analysed for total IgG using an MSD assay (using an anti-human IgGcapture antibody (Jackson) and a streptavidin-sulpho tag reveal antibody(MSD)). The inhibition curve was analysed by non-linear regression(Graphpad Prism®) to determine the EC₅₀. The graph represents combineddata from 6 or 7 experiments.

As shown in FIG. 4 CA170_01519.g57 Fab′ and CA170_01519.g57 Fab′PEGinhibit IgG recycling in a concentration dependent manner with mean EC₅₀values (n=6 or 7) of 1.937 nM and 6.034 nM respectively. Hence theCA170_01519.g57 Fab′PEG is approximately 3 fold less potent thanCA170_01519.g57 Fab′ in inhibiting IgG recycling.

CA170_01519.g57 Fab′PEG Inhibits the Transcytosis of Human IgG

FcRn can traffic IgG across polarised epithelial cell layers in both theapical to basolateral and basolateral to apical directions and thusplays an important role in permitting IgG to move between thecirculation and lumen at mucosal barriers (Claypool et al. 2004 Mol BiolCell 15(4):1746-59).

An in vitro assay was established to examine the ability ofCA170_01519.g57 Fab′PEG to inhibit FcRn dependent IgG transcytosis.Briefly, MDCK II clone 34 cells were plated in a 24 well transwell plateand allowed to form monolayers over 3 days. The cells were thenpre-incubated with CA170_01519.g57 Fab′PEG on the apical surface beforethe addition of biotinylated human IgG in an acidic buffer whichfacilitates binding to FcRn. The human IgG is transcytosed through thecells from the apical to basolateral side and released into a neutralbuffer in the lower chamber. Levels of IgG on the basolateral side werethen measured using an MSD assay.

FIG. 5 shows CA170_01519.g57 Fab′PEG inhibits apical to basolateral IgGtranscytosis in MDCK II clone 34 cells.

MDCK II clone 34 cells were plated at 500,000 cells per well of a 24well transwell plate and incubated for 3 days at 37° C., 5% CO₂ untilmonolayers were formed. The pH of the apical compartment was adjusted to5.9 and the basolateral side to 7.2 in a HBSS⁺ (Ca/Mg) buffer+1% BSA.Cells on the apical compartment were pre-incubated with CA170_01519.g57Fab′PEG for 1 hour before addition of 2.5 μg/ml biotinylated human IgG(Jackson) at the indicated concentrations for 4 hours at 37° C., 5% CO₂.The basolateral medium was then collected and total IgG measured by MSDassay (using an anti-human IgG capture antibody (Jackson) and astreptavidin-sulpho tag reveal antibody (MSD)). The inhibition curve wasanalysed by non-linear regression (Graphpad Prism®) to determine theEC₅₀. The graph represents combined data from 3 experiments.

In summary FIG. 5 shows that CA170_01519.g57 Fab′PEG can inhibit theapical to basolateral transcytosis of human IgG in a concentrationdependent manner with an EC₅₀ value of 25.5 nM (n=3).

Summary of In Vitro Effects of CA170_01519.g57 Fab′PEG

CA170_01519.g57 Fab′PEG inhibits both IgG recycling and transcytosis.The EC₅₀ of 6 nM achieved in the IgG recycling assay is comparable tothe cell affinity binding data in which K_(D) values of 6.5 nM inneutral buffer and 5.42 nM in acidic buffer were obtained.

CA170_01519.g57 Fab′PEG does show a slight reduction in potency comparedto the Fab′ alone, but compared to many of the other candidate moleculesassessed showed the lowest drop in potency between the two formats (seesupra). In the IgG transcytosis assay an EC₅₀ of 25.5 nM was obtained.

The data in this section have clearly shown that CA170_01519.g57 Fab′PEGcan inhibit human FcRn function.

Example 6 Cross Reactivity of CA170_01519.g57 Fab′PEG with Non-HumanPrimate FcRn

To validate the use of CA170_01519.g57 Fab′PEG in a non-human primatePK/PD study and pre-clinical toxicology, its relative affinity andfunctional potency with cynomolgus macaque FcRn was examined. MDCK IIcells stably transfected with cynomolgus macaque FcRn and B2M (MDCKII(cm)) were used for the following studies alongside the previouslydescribed MDCK II cells stably transfected with human FcRn and B2M (MDCKII clone 34).

Cell Based Affinity of CA170_01519.g57 Fab′PEG for Cynomolgus MonkeyFcRn

To determine the cell based binding affinity of CA170_01519.g57 Fab′PEGfor cynomolgus monkey FcRn, quantitative flow cytometry experiments wereperformed using MDCK II (cm) cells and AlexaFluor 488-labelledCA170_01519.g57 Fab′ or Fab′PEG. Specific binding of antibody tocynomolgus macaque FcRn across a range of antibody concentrations wasused to determine K_(D). Antibody binding was performed in both neutraland acidic pH to determine the effect of binding FcRn in neutral bloodplasma or acidic endosomes and to therefore determine any effect pH mayhave on CA170_01519.g57 binding to cynomolgus macaque FcRn.

FIG. 6 — shows CA170_01519.g57 Fab′ (A) and CA170_01519.g57 Fab′PEG (B)binding on MDCK II (cm) cells in acidic and neutral pH.

MDCK II (cm) cells were incubated in Facs buffer (PBS with 0.2% w/v BSA,0.09% w/v NaN3) for 30 mins prior to the addition of Alexa-fluor 488labelled CA170_01519.g57 Fab′ or Fab′PEG for 1 hour in Facs buffer ateither pH 7.4 or pH 6. The final antibody concentrations ranged from 931nM to 0.002 nM. The cells were washed in ice cold Facs buffer thenanalysed by flow cytometry using a Guava flow cytometer (Millipore, UK).Titration data sets were also produced for isotype control antibodiesfor each antibody format to determine non specific binding. The numberof moles of bound antibody was calculated by using interpolated valuesfrom a standard curve generated from beads carrying varying amounts offluorescent dye. Geometric mean fluorescence values were determined inthe flow cytometric analyses of cells and beads. Non-specific bindingwas subtracted from the anti-FcRn antibody values and the specificbinding curve generated was analysed by non-linear regression using aone-site binding equation (Graphpad Prism®) to determine the K_(D). Datais representative of between 2 and 3 experiments.

TABLE 5 Mean K_(D) values (nM) for CA170_01519.g57 Fab' & Fab'PEG onMDCKII (cm) cells. Antibody format Cyno FcRnpH 7.4 Cyno FcRnpH 6.01519.g57 Fab' 1.16 1.09 1519.g57 Fab'PEG 8.15 5.01

FIG. 6 shows representative binding curves for CA17001519.g57 Fab′ (FIG.6A) and Fab′PEG (FIG. 6B) binding to cynomolgus macaque FcRn. The meanK_(D) values obtained for CA17001519.g57 Fab′ and Fab′PEG are shown inTable 5. These values are comparable to the K_(D) values obtained forCA170_01519.g57 Fab′ and Fab′PEG binding to human FcRn (see table 4)

CA170_01519.g57 Fab′PEG Inhibits the Recycling of Cynomolgus Monkey IgG

To determine if CA170_01519.g57 Fab′PEG is functionally active inblocking cynomolgus monkey FcRn, MDCK II (cm) cells were used to examinethe ability of CA170_01519.g57 Fab′PEG to inhibit the recycling ofcynomolgus macaque IgG as described previously for the human FcRn assay.The assay was run alongside representative human assays to allow for acomparison between the two.

Briefly, MDCK II cells (clone 34 or cm) were pre-incubated withCA170_01519.g57 Fab′PEG before addition of biotinylated human (h) orcynomolgus macaque (c) IgG in an acidic buffer to allow binding to FcRn.All excess CA170_01519.g57 Fab′PEG and biotinylated IgG were removed andthe cells incubated in a neutral pH buffer to allow release of IgG intothe supernatant. The inhibition of FcRn was assessed by detecting theamount of IgG present in the supernatant by MSD assay and percentinhibition calculated.

As shown in FIG. 7 , CA170_01519.g57 Fab′PEG can inhibit both human andcynomolgus macaque IgG recycling in a concentration dependent manner,with EC₅₀ values of 8.448 nM and 5.988 nM respectively. Inhibition ofFcRn by CA170_01519.g57 Fab′PEG in the human and cynomolgus macaqueassays are comparable, although it appears slightly more potent againstthe cynomolgus FcRn.

TABLE 6 1519.g57 Fab'PEG 1519.g57 Fab'PEG hF cRn:hIgG cFcRn:clgG EC 50(nM) 6.448 5.988 95% CT (nM) 6.560 to 10.88 5.283 to 6.6561

FIG. 7 shows CA170_01519.g57 inhibits IgG recycling in MDCK II clone 34cells & MDCK II (cm) cells.

MDCK II clone 34 and MDCK II (cm) cells were plated at 25,000 cells perwell in a 96 well plate and incubated overnight at 37° C., 5% CO₂. Thecells were pre-incubated with CA170_01519.g57 Fab′ or Fab′PEG in HBSS⁺(Ca/Mg) pH 5.9+1% BSA for 1 hour at 37° C., 5% CO₂ before addition of500 ng/ml of biotinylated human or cyno IgG and incubated for a further1 hour. The cells were then washed with HBSS⁺ pH 5.9 and incubated at37° C., 5% CO₂ for 2 hours in HBSS⁺ pH 7.2. The supernatant was removedfrom the cells and analysed for total IgG using an MSD assay (using ananti-human IgG capture antibody (Jackson) and a streptavidin-sulpho tagreveal antibody (MSD)). The inhibition curve was analysed by non-linearregression (Graphpad Prism®) to determine the EC₅₀. The graph representscombined data from 2 experiments.

Example 7 Effect of 01519g Fab PEG in Cynomolgus Monkey

This was a study of the effect of the administration of 01519g Fab PEGin cynomolgus monkeys, in single, intermittent or repeated dosingregimens. 01519g Fab PEG was administered by intravenous infusion, as asingle dose or in repeat doses to groups of four cynomolgus monkeys asindicated in Table 7. Plasma IgG and the pharmacokinetics of the 01519gFab PEG were monitored by immunoassay (see Table 7A for immunoassaymethods) and LC-MS/MS. Assay of plasma albumin was conducted at Covance.

TABLE 7 Dose groups in study NCD2241. Dosing was by intravenousinfusion. The redose was the same as the first dose in each case. Repeatdoses (4 of) were weekly. Dose Dosing Phase Group Antibody (mg/kg)Regimen Comments I 1 Control 0 Single Dose Redose at 67 days 2 Fab PEG20 Single Dose Redose at 67 days 3 Fab PEG 100 Single Dose Redose at 67days II 4 Control 0 Repeat Dose 5 Fab PEG 20 Repeat Dose 6 Fab PEG 100Repeat Dose

TABLE 7A Plasma IgG, PK and ADA immunoassay methods Assay typeImmunoassay Method PD Total plasma 1) Coat immunoassay plate withF(ab')₂ IgG goat anti-human Fcγ 2) Incubate with sample. 3) Reveal withhorseradish peroxidase conjugated F(ab')₂, goat anti-human IgG F(ab')₂ &the addition of TMB substrate. PK Fab PEG PK 1) Coat immunoassay platewith FcRn. 2) Incubate with sample. 3) Reveal with biotin conjugatedmurine IgGl anti-PEG/ .Streptavidin-horseradish peroxidase conjugate &the addition of TMB substrate alternatively reveal with MSD sulfo-taggedgoat anti-human kappa & the addition of MSD read buffer

Effect on Plasma IgG Concentration

Immunoassay and LC-MS/MS plasma IgG data were in good agreement. PlasmaIgG was reduced by the administration of Fab PEG (see FIG. 12 and FIG.14 ). For both Phase I dose groups, a single dose of Fab PEG reducedplasma IgG by approximately 70-80%, reaching a nadir at approximately 7days and returning to pre-dosing levels by day 63. Redosing at day 67achieved similar results.

For both Phase II dose groups, 4 weekly doses of the Fab PEG reducedplasma IgG by approximately 70-80%, again reaching a nadir at about 7days after the first dose. The results are shown in FIG. 13 .

Example 8 Effect of CA170_01519.g57 Fab′PEG and CA170_01519.g57 IgG4P inCynomolgus Monkeys

The effects of CA170_01519g.57 Fab′PEG and CA170_01519g.57 IgG4P onendogenous plasma IgG were determined in cynomolgus monkeys. Animalswere dosed as indicated in Table 8, with 4 animals per treatment group.Plasma IgG and the pharmacokinetics of the anti-FcRn entities weremonitored by immunoassay (see Table 8A for immunoassay methods) andLC-MS/MS.

TABLE 8 Treatment regimens in cynomolgus monkeys. Anti- Dose FcRn(mg/kg) Dosing Regimen Route FIG. Fab'PEG 20 Day 0 & 65 i.v. 15 Fab'PEG20 Every 3 days, day 0-27 i.v. 16 IgG4P 30 Day 0 & 63 i.v. 17 IgG4P 30 &5 30 mg/kg on day 0, i.v. 18 5 mg/kg daily day 1-41 Control 0 Daily day0-41 i.v. 19

TABLE 8A Plasma IgG and PK immunoassay methods Assay type ImmunoassayMethod PD Total plasma 1) Coat immunoassay plate with F(ab')2 Goat anti-IgG human Fcγ. 2) Incubate with sample. 3) Reveal with horseradishperoxidase conjugated F(ab')2, goat anti-human IgG F(ab')2 and theaddition of TMB substrate. PK Fab’PEG PK 1) Coat MSD streptavidin platewith biotinylated FeRn. 2) Incubate with sample. 3) Reveal with MSDsulfo-tagged goat anti-human kappa and the addition of MSD read buffer.

Effect on Plasma IgG Concentration.

Immunoassay and LC-MS/MS plasma IgG data were in good agreement. PlasmaIgG was reduced by the administration of anti-FcRn Fab′PEG or anti-FcRnIgG4P (see FIGS. 15 and 16 and FIGS. 17 and 18 respectively; see FIG. 19for control). For both anti-FcRn entities, a single dose reduced plasmaIgG by approximately 70-80%, reaching a nadir at approximately 7 daysand returning to pre-dosing levels by day 62. Redosing at day 63 or day65, as described achieved similar results.

Repeated dosing of anti-FcRn Fab′PEG or IgG4P reduced plasma IgG byapproximately 60-80% and maintained the level of IgG for the duration ofthe dose period. Again, the nadir was reached at about 7 days after thefirst dose. The results are shown in FIGS. 16 and 18 .

Example 9 Effect of CA170_01519.g57 Fab′PEG, CA170_01519.g57 IgG1,CA170_01519.g57 IgG4P, CA170_01519.g57 Fab′HSA, CA170_01519.g57 FabFvand CA170_01519.g57 Fab in hFcRn Transgenic Mice

The effect of various different formats of antibody CA170_01519.g57 onthe clearance of human IVIG was determined in human FcRn transgenicmice. The formats tested were CA170_01519.g57 Fab′PEG, CA170_01519.g57IgG1, CA170_01519.g57 IgG4P, CA170_01519.g57 Fab′HSA, CA170_01519.g57FabFv and CA170_01519.g57 Fab and the results and are shown in FIGS. 20,21, 22, 23 and 24 respectively. The single doses of active compound wereas shown in the Figures. In order to detect their effects on theclearance of human IgG (IVIG), the mice were injected with 500 mg/kghuman IVIG which was quantified by LCMSMS in serial plasma sampleswithdrawn from the tails of the mice at intervals. Blocking of hFcRn byeach of the different antibody formats tested resulted in acceleratedclearance of hIVIG and lower concentrations of total IgG were observedcompared to control mice.

Anti-FcRn Treatment Enhances the Clearance of hIgG in hFcRn TransgenicMice

Humanised FcRn transgenic mice (B6.Cg-Fcgrt^(tmlDcr)Tg(FCGRT)32Dcr/DcrJ, JAX Mice) were infused intravenously with 500 mg/kghuman IgG (Human IgI 10% Gamunex-c, Talecris Biotherapeutics). 24 hourslater animals were dosed with vehicle control (PBS) or anti-FcRnintravenously as a single dose. Tail tip blood samples were taken at−24, 8, 24, 48, 72, 144 and 192 hours relative to anti-FcRn treatment.Serum levels of human IgG in the hFcRn mouse and the pharmacokinetics ofFcRn inhibitors were determined by LC-MS/MS. Data presented in FIGS. 20to 24 are mean±SEM with 3-6 mice per treatment group.

Quantification of Human IgG, Endogenous Cynomolgus IgG and FcRnInhibitors by LC-MS/MS

Human IgG, cynomolgus IgG and FcRn inhibitors (1519.g57 Fab′PEG,1519.g57 IgG4P, 1519.g57 IgG1, 1519.g57 FabFv, 1519.g57 Fab and 1519.g57Fab′HAS) were quantified using liquid chromatography tandem massspectrometry (LC-MS/MS) analysis following tryptic digestion.

Quantitation was achieved by comparison to authentic standard materialspiked at known concentrations into blank matrix, with spiked horsemyoglobin used as the internal standard. Unique (“proteotypic”) peptidesfor all analytes of interest investigated were selected and both samplesand calibration samples were tryptically digested as outlined below. Inbrief, tryptic digest of 5 μl serum samples was performed overnightusing Sequencing Grade Modified Trypsin (Promega, Southampton, UK)following denaturation with acetonitrile/tris (2-carboxyethyl) phosphineand carbamido-methylation with iodoacetamide (all from Sigma-Aldrich,Poole, UK).

Analytes were separated using an Onyx Monolithic C18 column (100×4.6 mm,Phenomenex, Macclesfield, UK) with a gradient of 2 to 95% (v/v)water/acetonitrile (0.1% formic acid) delivered at 1.5 mL/min over 6minutes.

The injection volume was 10 μL; all of the eluent was introduced intothe mass spectrometer source.

The source temperature of the mass spectrometer was maintained at 600°C. and other source parameters (e.g. collision energy, declusteringpotential, curtain gas pressure etc.) were optimized to achieve maximumsensitivity for each peptides of interest. Selective transitions foreach proteotypic peptide of interest were monitored.

Example 10: Crystallography and Binding Epitope

The crystal structure of 1519g57 Fab′ and deglycosylated human FcRnextracellular domain (alpha chain extracellular domain (SEQ ID NO:94) inassociation with beta2 microglobulin SEQ ID NO:95) was determined, withthe FcRn oligsaccharide excluded in order to facilitate crystallization.1519.g57 Fab′ was reacted with 10-fold molar excess of N-ethyl maleimideto prevent formation of diFab′ and any existing diFab′ removed by SEC(S200 on Akta FPLC). Human FcRn extracellular domain was treated byPNGaseF to remove N-linked sugars. For this, the FcRn sampleconcentration was adjusted using PBS (pH7.4) to 5 mg/ml and a totalvolume of 1 ml. 200 units of PNGaseF (Roche) was added to this solutionof human FcRn. This was incubated at 37° C. for ˜18 hours, followingwhich the extent of deglycosylation was checked using SDS PAGE. Uponcompletion of the reaction the deglycosylated FcRn was buffer exchangedinto 50 mM Sodium Acetate, 125 mM NaCl, pH6.0.

The complex was formed by incubation of a mixture of reagents(Fab′:FcRn::1.2:1, w/w) at room temperature for 60 minutes, and thenpurified using SEC (S200 using Akta FPLC). Screening was performed usingthe various conditions that were available from Qiagen (approximately2000 conditions). The incubation and imaging was performed byFormulatrix Rock Imager 1000 (for a total incubation period of 21 days).The result of screening is shown in Tables 9, 10 and 11 (see FIG. 26 ).

TABLE 9 The result of crystallisation screening, showing the crystalused for X-ray analysis Crystallization experiment type Sitting drop,vapour diffusion Crystallization condition 0.1 M Sodium citrate pH5.5,11% PEG6000 Protein concentration 10 mg/ml Drop volume/ratio 0.4 ulProtein + 0.4 ul Reservoir Crystal growth time 8-21 days CryoprotectionCrystals were harvested from the drop, transferred to cryoprotectionbuffer (70% reservoir + 30% ethylene glycol) and flash-frozen in liquidnitrogen (−180° C.) within 10 seconds.

TABLE 10 Conditions for collection and processing of X-ray analysisdata. X-ray source Diamond Light Source, Beamline 104 Experiment TypeSingle-wavelength Wavelength 0.9795 Å Processing Software Mosflm/ScalaResolution Limits 35.00-2.90 Space group P3₂ 2 1 Unit Cell a = 150.10 Åb = 150.10 Å c = 89.15 Å parameters α = 90.00° β = 90.00° γ = 120.00 °Completeness 99.9% (100.0%) Multiplicity 6.7 (6.8) I/σ(I) 13.4 (4.8)Rmerge 9.2% (36.3%) Number of 172724 (25602) Number of unique 25967(3760) reflections reflections Comments Note: Numbers in parenthesisrefer to the outer resolution shell

TABLE 11 Structure determination and refinement. Structure determinationMolecular method Replacement Program(s) used Phaser Structure templateStructure FcRn receptor from PDB 3M17 and previously solved Fab- 3DVNRefinement program Refmac5 Resolution limits 30.00-2.9 R factor 23.2%Free R factor 28.4% Number of non-hydrogen atoms 6125 protein atoms 2Acetate ions (4 atoms each) 27 waters in AU 2 Cl⁻ ions 2 Na⁺ ions RMSDbond length 0.009 Å RMSD bond angle 1.338° Ramachandran allowed 98.6%Ramachandran outliers 1.4% Comments Rebuilt using CCP4/Coot.

There was no obvious change in FcRn structure upon binding of 1519g57Fab′ (comparing this complex with published structures of FcRn). Fromthe crystal structure it the secondary structure content was calculatedto be: α-helix 9.4%; β-sheet 45.2%; 3-10 turn 2.5%.

The residues interacting with 1519g57 Fab′ were all in the FcRn a chain(not (32M) and are indicated below in bold. The residues concernedencompass all but 1 of the residues critical for binding Fc. 1519g57binds in a region that overlays the Fc-binding region, suggesting thatblockade of FcRn by 1519g57 Fab′ is by simple competition, the anti-FcRnbeing effective by virtue of its superior affinity.

(SEQ ID NO: 94) AESHLSLLYH LTAVSSPAPG TPAFWVSGWL GPQQYLSYNSLRGEAEPCGA WVWENQVSWY WEKETTDLRI KEKLFLEAFKALGGKGPYTL QGLLGCELGP DNTSVPTAKF ALNG EEF MNFDLKQGTWGGD WPEALAISQR WQQQDKAANK ELTFLLFSCPHRLREHLERG RGNLEWKEPP SMRLKARPSS PGFSVLTCSAFSFYPPELQL RFLRNGLAAG TGQGDFGPNS DGSFHASSSLTVKSGDEHHY CCIVQHAGLA QPLRVELESPAKSS

The FcRn a chain sequence, showing residues involved in interaction with1519g57 Fab′ (bold) and residues critical for interaction with Fc of IgG(underlined). All but 1 of the latter are included in the former.

The ASCII text file named “CELL0017-100-DIV-2 Sequence Listing,” createdon May 31, 2022, comprising 127 kilobytes, is hereby incorporated byreference in its entirety.

1. An isolated DNA molecule or a pair of isolated DNA molecules encodingthe heavy and light chains of an anti-FcRn antibody or FcRn-bindingfragment thereof, wherein the heavy chain comprises three CDRs, whereinCDR H1 has the sequence given in SEQ ID NO: 1, CDR H2 has the sequencegiven in SEQ ID NO: 2, and CDR H3 has the sequence given in SEQ ID NO:3, and the light chain comprises three CDRs, wherein CDR L1 has thesequence given in SEQ ID NO: 4, CDR L2 has the sequence given in SEQ IDNO: 5 and CDR L3 has the sequence given in SEQ ID NO:
 6. 2. The isolatedDNA molecule or pair of isolated DNA molecules according to claim 1,wherein the antibody is humanized.
 3. The isolated DNA molecule or pairof isolated DNA molecules according to claim 1, wherein the heavy chaincomprises the sequence given in SEQ ID NO: 29 and the light chaincomprises the sequence given in SEQ ID NO:
 15. 4. The isolated DNAmolecule or pair of isolated DNA molecules according to claim 1, whereinthe heavy chain comprises a sequence having at least 90% identity to thesequence given in SEQ ID NO: 29 and wherein the light chain comprises asequence having at least 90% identity to the sequence given in SEQ IDNO:
 15. 5. The isolated DNA molecule or pair of isolated DNA moleculesaccording to claim 1, wherein the FcRn-binding fragment is a scFv, Fv,Fab or Fab′ fragment.
 6. The isolated DNA molecule or pair of isolatedDNA molecules according to claim 6, wherein the FcRn-binding fragment isa Fab′ fragment having a heavy chain comprising the sequence given inSEQ ID NO: 36 and a light chain comprising the sequence given in SEQ IDNO:
 22. 7. The isolated DNA molecule or pair of isolated DNA moleculesaccording to claim 1, wherein the anti-FcRn antibody is a full lengthantibody.
 8. The isolated DNA molecule or pair of isolated DNA moleculesaccording to claim 7, wherein the full length antibody is selected fromthe group consisting of an IgG1, IgG4 and IgG4P.
 9. The isolated DNAmolecule or pair of isolated DNA molecules according to claim 8, whereinthe antibody has a heavy chain comprising the sequence given in SEQ IDNO: 72, SEQ ID NO: 87 or SEQ ID NO: 43 and a light chain comprising thesequence given in SEQ ID NO:
 22. 10. The isolated DNA molecule or pairof isolated DNA molecules according to claim 1, wherein the antibody orbinding fragment thereof is a Fab-dsFv having a heavy chain comprisingthe sequence given in SEQ ID NO: 50 and a light chain comprising thesequence given in SEQ ID NO: 46 or SEQ ID NO:
 78. 11. The isolated DNAmolecule or pair of isolated DNA molecules according to claim 1, whereinthe anti-FcRn antibody or FcRn-binding fragment thereof binds humanFcRn.
 12. The isolated DNA molecule or pair of isolated DNA moleculesaccording to claim 11, wherein the anti-FcRn antibody or FcRn-bindingfragment thereof blocks binding of human IgG to human FcRn.
 13. Theisolated DNA molecule or pair of isolated DNA molecules according toclaim 1, wherein the anti-FcRn antibody or FcRn-binding fragment thereofdoes not bind β2 microglobulin.
 14. A cloning or expression vector or apair of cloning or expression vectors encoding the heavy and lightchains of an anti-FcRn antibody or FcRn-binding fragment thereof,wherein the heavy chain comprises three CDRs, wherein CDR H1 has thesequence given in SEQ ID NO: 1, CDR H2 has the sequence given in SEQ IDNO: 2, and CDR H3 has the sequence given in SEQ ID NO: 3, and the lightchain comprises three CDRs, wherein CDR L1 has the sequence given in SEQID NO: 4, CDR L2 has the sequence given in SEQ ID NO: 5 and CDR L3 hasthe sequence given in SEQ ID NO:
 6. 15. The cloning or expression vectoror pair of cloning or expression vectors according to claim 14, whereinthe antibody is humanized.
 16. The cloning or expression vector or pairof cloning or expression vectors according to claim 14, wherein theheavy chain comprises the sequence given in SEQ ID NO: 29 and the lightchain comprises the sequence given in SEQ ID NO:
 15. 17. The cloning orexpression vector or pair of cloning or expression vectors according toclaim 14, wherein the heavy chain comprises a sequence having at least90% identity to the sequence given in SEQ ID NO: 29 and wherein thelight chain comprises a sequence having at least 90% identity to thesequence given in SEQ ID NO:
 15. 18. The cloning or expression vector orpair of cloning or expression vectors according to claim 14, wherein theFcRn-binding fragment is a scFv, Fv, Fab or Fab′ fragment.
 19. Thecloning or expression vector or pair of cloning or expression vectorsaccording to claim 18, wherein the FcRn-binding fragment is a Fab′fragment having a heavy chain comprising the sequence given in SEQ IDNO: 36 and a light chain comprising the sequence given in SEQ ID NO: 22.20. The cloning or expression vector or pair of cloning or expressionvectors according to claim 14, wherein the anti-FcRn antibody is a fulllength antibody.
 21. The cloning or expression vector or pair of cloningor expression vectors according to claim 20, wherein the full lengthantibody is selected from the group consisting of an IgG1, IgG4 andIgG4P.
 22. The cloning or expression vector or pair of cloning orexpression vectors according to claim 21, wherein the antibody has aheavy chain comprising the sequence given in SEQ ID NO: 72, SEQ ID NO:87 or SEQ ID NO: 43 and a light chain comprising the sequence given inSEQ ID NO:
 22. 23. The cloning or expression vector or pair of cloningor expression vectors according to claim 14, which comprises (i) thesequence given in SEQ ID NO: 37 and the sequence given in SEQ ID NO: 23or (ii) the sequence given in SEQ ID NO: 80 and the sequence given inSEQ ID NO: 79, or (iii) the sequence given in SEQ ID NO: 93 and thesequence given in SEQ ID NO:
 91. 24. The cloning or expression vector orpair of cloning or expression vectors according to claim 14, wherein theanti-FcRn antibody or FcRn-binding fragment thereof binds human FcRn.25. The cloning or expression vector or pair of cloning or expressionvectors according to claim 24, wherein the anti-FcRn antibody orFcRn-binding fragment thereof blocks binding of human IgG to human FcRn.26. The cloning or expression vector or pair of cloning or expressionvectors according to claim 14, wherein the anti-FcRn antibody orFcRn-binding fragment thereof does not bind (32 microglobulin.
 27. Ahost cell comprising a cloning or expression vector or a pair of cloningor expression vectors encoding the heavy and light chains of ananti-FcRn antibody or FcRn-binding fragment thereof, wherein the heavychain comprises three CDRs, wherein CDR H1 has the sequence given in SEQID NO: 1, CDR H2 has the sequence given in SEQ ID NO: 2, and CDR H3 hasthe sequence given in SEQ ID NO: 3, and the light chain comprises threeCDRs, wherein CDR L1 has the sequence given in SEQ ID NO: 4, CDR L2 hasthe sequence given in SEQ ID NO: 5 and CDR L3 has the sequence given inSEQ ID NO:
 6. 28. The host cell according to claim 27, wherein theantibody is humanized.
 29. The host cell according to claim 27, whereinthe heavy chain comprises the sequence given in SEQ ID NO: 29 and thelight chain comprises the sequence given in SEQ ID NO:
 15. 30. The hostcell according to claim 27, wherein the heavy chain comprises a sequencehaving at least 90% identity to the sequence given in SEQ ID NO: 29 andwherein the light chain comprises a sequence having at least 90%identity to the sequence given in SEQ ID NO:
 15. 31. The host cellaccording to claim 27, wherein the FcRn-binding fragment is a scFv, Fv,Fab or Fab′ fragment.
 32. The host cell according to claim 31, whereinthe FcRn-binding fragment is a Fab′ fragment having a heavy chaincomprising the sequence given in SEQ ID NO: 36 and a light chaincomprising the sequence given in SEQ ID NO:
 22. 33. The host cellaccording to claim 31, wherein the FcRn-binding fragment is a Fab-dsFvfragment having a heavy chain comprising the sequence given in SEQ IDNO: 50 and a light chain comprising the sequence given in SEQ ID NO: 46or
 78. 34. The host cell according to claim 31, wherein the anti-FcRnantibody is a full length antibody.
 35. The host cell according to claim34, wherein the full length antibody is selected from the groupconsisting of an IgG1, IgG4 and IgG4P.
 36. The host cell according toclaim 35, wherein the anti-FcRn antibody has a heavy chain comprisingthe sequence given in SEQ ID NO: 72, SEQ ID NO: 87 or SEQ ID NO: 43 anda light chain comprising the sequence given in SEQ ID NO:
 22. 37. Thehost cell according to claim 27, wherein the anti-FcRn antibody orFcRn-binding fragment thereof binds human FcRn.
 38. The host cellaccording to claim 37, wherein the anti-FcRn antibody or FcRn-bindingfragment thereof blocks binding of human IgG to human FcRn.
 39. The hostcell according to claim 27, wherein the anti-FcRn antibody orFcRn-binding fragment thereof does not bind (32 microglobulin.
 40. Aprocess for the production of an anti-FcRn antibody or FcRn-bindingfragment thereof, the process comprising culturing a host cell thatcomprises a cloning or expression vector or a pair of cloning orexpression vectors encoding the heavy and light chains of an anti-FcRnantibody or FcRn-binding fragment thereof and isolating said antibody orfragment, wherein the heavy chain comprises three CDRs, wherein CDR H1has the sequence given in SEQ ID NO: 1, CDR H2 has the sequence given inSEQ ID NO: 2, and CDR H3 has the sequence given in SEQ ID NO: 3, and thelight chain comprises three CDRs, wherein CDR L1 has the sequence givenin SEQ ID NO: 4, CDR L2 has the sequence given in SEQ ID NO: 5 and CDRL3 has the sequence given in SEQ ID NO:
 6. 41. The process of claim 40,wherein the antibody is humanized.
 42. The process of claim 40, whereinthe heavy chain comprises the sequence given in SEQ ID NO: 29 and thelight chain comprises the sequence given in SEQ ID NO:
 15. 43. Theprocess of claim 40, wherein the heavy chain comprises a sequence havingat least 90% identity to the sequence given in SEQ ID NO: 29 and whereinthe light chain comprises a sequence having at least 90% identity to thesequence given in SEQ ID NO:
 15. 44. The process of claim 40, whereinthe FcRn-binding fragment is a scFv, Fv, Fab or Fab′ fragment.
 45. Theprocess of claim 44, wherein the FcRn-binding fragment is a Fab′fragment having a heavy chain comprising the sequence given in SEQ IDNO: 36 and a light chain comprising the sequence given in SEQ ID NO: 22.46. The process of claim 44, wherein the FcRn-binding fragment is aFab-dsFv fragment having a heavy chain comprising the sequence given inSEQ ID NO: 50 and a light chain comprising the sequence given in SEQ IDNO: 46 or
 78. 47. The process of claim 40, wherein the anti-FcRnantibody is a full length antibody.
 48. The process of claim 47, whereinthe full length antibody is selected from the group consisting of anIgG1, IgG4 and IgG4P.
 49. The process of claim 48, wherein the anti-FcRnantibody has a heavy chain comprising the sequence given in SEQ ID NO:72, SEQ ID NO: 87, or SEQ ID NO: 43 and a light chain comprising thesequence given in SEQ ID NO:
 22. 50. The process according to claim 40,wherein the anti-FcRn antibody or FcRn-binding fragment thereof bindshuman FcRn.
 51. The process according to claim 50, wherein the anti-FcRnantibody or FcRn-binding fragment thereof blocks binding of human IgG tohuman FcRn.
 52. The process according to claim 40, wherein the anti-FcRnantibody or FcRn-binding fragment thereof does not bind β2microglobulin.